Jupiter: The Giant Planet, 07 November 2015
On 07 November 2015, renowned astro-imager Damien Peach lectured to members of OASI on Jupiter: The Giant Planet. Damien reviewed the history of efforts to record features on the disk of the planet, from 17th century line drawings through to modern astrophotography. Speaking for 38 minutes and then taking questions, he followed the old adage "leave them wanting more". The photographs below, by John Wainwright, show OASI Chairman David Murton introducing Damien at the start of the lecture, and the packed lecture room.
Lunatick Astronomy, 11 September 2015
On 11 September 2015, Andrew Lound entertained members of OASI with one of the most innovative lectures to the Society of recent years, in the form of a one-man dramatical presentation rather than a traditional lecture. The photograph below, by John Wainwright, shows Andrew in historical costume during the event.
Using the Sloan Digital Sky Survey to Study Quasars and the Early Universe, 21 November 2014
On 21 November 2014, OASI member Alan Mcguire presented a fascinating talk entitled "Using the Sloan Digital Sky Survey to Study Quasars and the Early Universe". The upstairs meeting room of the Methodist Church Hall was well attended for what was an excellent talk.
Photos below by John Wainwright show the scene during a coffee break mid-lecture.
Black Swans In Cygnus, 24 October 2014
On 24 October 2014, Professor Ralph Spencer presented a fascinating talk entitled "Black Swans", about black holes in the constellation Cygnus. The upstairs meeting room of the Methodist Church Hall was well attended for what was an excellent talk.
Photos below by John Wainwright show the scene during the coffee break at the end of the lecture.
Building the Solar System, 21 February 2014
On 21 February 2014, Greg Smye-Rumsby (of the Royal Observatory and "Astronomy Now") presented a fascinating talk entitled "Building the Solar System". The upstairs meeting room of the Methodist Church Hall was well attended for the event and members present were not disappointed, as Greg brought everyone up to date on the latest theoretical developments in this fascinating area of science.
Photos below by John Wainwright.
Presidential Lecture, 07 June 2013
On 07 June 2013, Dr Allan Chapman delivered the sixth OASI Presidential Lecture in the delightful setting of the Orangerie at Orwell Park School. Allan took as his subject Patrick Moore, A Lifetime In Astronomy and kept members of OASI and their guests, an audience of 50 in total, enthralled as he described the life and times of his late, great friend, Patrick. Allan placed Patrick's work firmly in its historical context, drawing many parallels with the great communicators of science and astronomy of the past, as far back as John Wilkins (1614-72), a founder of the Royal Society.
Photos below are by Martin Cook, Mike Norris, Martin Richmond-Hardy and John Wainwright.
Presidential Lecture, 04 May 2007
The fourth OASI Presidential Lecture, delivered by Professor Allan Chapman on 04 May 2007, was, perhaps predictably, a resounding success and thoroughly enjoyed by all, not least by Allan himself. The audience included members of OASI and their guests, delegates from neighbouring astronomical societies and local leading amateur astronomers Tom Boles and Martin Mobberley.
Appropriately in OASI's 40th year, Allan's ninety plus minute lecture was entitled That Clubbable Passion, the Amateur Astronomical Society. Allan took the title from his ground breaking 1998 book The Victorian Amateur Astronomer, of which a second edition is due to be re-printed later in 2007. Allan firstly set the socio-economic background to astronomical endeavour across Europe from Georgian times through to the present day. Science in Europe outside the UK received funding through government or from the sovereign. However, astronomical research in the UK was the realm of the private individual and it was not before Sir George Airy's appointment as Astronomer Royal in 1836 that salaried science began to be the norm in this country1. Allan described some amateur astronomers, ranging from grand amateurs such as the 3rd Earl of Rosse, to grand patrons such as Colonel Tomline of Orwell Park, to the country parson style of amateur such as the Rev T W Webb, through to dedicated amateurs of limited means, nonetheless pursuing valuable work. The grand amateurs had the time and financial resource to pursue their love of the night sky at rates of expenditure that stand comparison with funding provided in modern times by governments. Lord Rosse, for example, built the world's largest telescope (it remained such for over 72 years) at his seat at Birr Castle in Ireland. He used the instrument's power primarily to resolve the nature of nebulae. William Lassell made a fortune selling beer to the dock workers of Liverpool and then took early retirement to pursue astronomy full time; with his revolutionary equatorially mounted 60 cm reflector he discovered Neptune's large moon Triton on 10 October 1846, less than a month after the discovery of the planet itself. Colonel Tomline, who built a private observatory and employed a professional astronomer to run it, was typical of the grand patrons. The most prominent of the country parson style of middle-class amateurs was the Rev T W Webb of Hardwick, Herefordshire, whose 1859 publication Celestial Objects for Common Telescopes was the first book of real use to the amateur, offering advice on celestial objects within range of the primary instrument of the day - the then ubiquitous 75 mm brass-tube refractor. Among the so-called lower echelons of society there were dedicated amateurs of little education or wealth such as Roger Langdon, the station master of Silverton in Devon, who, between his many duties such as selling tickets, sweeping platforms and seeing the trains in and out, undertook serious astronomical research from his garden observatory at the side of the station.
Allan suggested that aside from the group of middle class gentlemen who met first in the Lincoln's Inn area of London in 1820 and whose burgeoning membership would within a few years become the Royal Astronomical Society, the first amateur grouping as we would understand it today was that of Admiral Smyth of Bedford and Dr John Lee of Hartwell House Mansion at Aylesbury, who held well-attended weekend observing parties at Hartwell House in the early Victorian era - the so-called Bedford/Aylesbury Axis.
The first truly recognisable astronomical society was that at Leeds, which had formed following a lecture there in 1858 by Sir John Herschel - son of Sir William Herschel. The society flourished for a few short years, but foundered some time before the first of the long-lasting groups formed at Liverpool. From around 1859, informal astronomical groups were springing up in many towns and cities around Great Britain and thereafter, "household name" astronomical groups began to appear in major population centres, notably Manchester, Leeds (again) and Cardiff. By 1890 the British Astronomical Association had been founded - and continues to go from strength to strength!
After answering questions (not that Allan had left much ground uncovered!) a celebratory OASI birthday cake was brought to the front of the audience and Allan, along with long-serving OASI member (now trustee of the Society) Roy Adams was invited to blow out the candles and cut the cake. This proved to be a repeat of the biblical feeding of the 5,000 given the excellent turnout! Light refreshments to wash down the cake were ably organised by Pete Richards and Nikky Gillard with assistance from Martin Cook, for which all attendees were most grateful.
Before Allan's lecture began, I had set the scene by explaining the origins of OASI and touching upon our predecessors, the Ipswich & District Astronomical Association (IDAS) which had flourished in the late 1940s - early 1950s and before IDAS a branch of the Chaldaean Society in the 1920s and early 1930s. Whilst we are able to say for sure that OASI formed in 1967, we cannot offer an exact date within that year. The cake, therefore, was something of a token for the year itself and Allan's lecture seemed the most appropriate point at which to celebrate the anniversary.
On the morning following Allan's lecture, I collected him from his hotel and we drove to Playford so that he could see for himself the beautifully restored headstones in the Airy family burial plot in St Mary's churchyard. Allan placed some flowers on the graves and then we were off to Bury St Edmunds to honour a long-standing invitation for Allan to visit the rooftop observatory on the Athenaeum building on Angel Hill. This well preserved Victorian time capsule of an observatory is in many respects a classic example of the mid 19th century interest in astronomy. Martin Mobberley and I, with valued initial help from Garry Coleman, undertook many months of research (mostly undertaken by Martin) into the observatory, after which we co-authored a paper on it in the Journal of the British Astronomical Association (JBAA) in October 20052.
The observatory was built in 1859 following a public lecture at the Athenaeum by Airy and the coincidental apparition of Donati's Comet in the autumn of 1858. It was paid for by public donation and is today very much in original condition with its 100 mm Troughton & Simms Refractor, the purchase of which Airy had negotiated directly from William Simms for £100. However, today the fabric of the building in the area immediately around the dome is in need of major overhaul and a lack of even the most basic handrails and safety features render the area out of bounds to the public and very much the stuff of a health and safety inspector's worst nightmare! Allan, Martin and I had exceptional special permission to visit the observatory.
Astronomical pursuits constitute a broad spectrum of activity and from the very old in Bury St Edmunds, our trio went to the very new - to Martin Mobberley's observatory at Cockfield3. Martin is a former BAA President and a very active observer. His many articles in Astronomy Now, Sky at Night and JBAA bear testament to the fact that his main interest is CCD imaging of comets and other deep sky objects and his main instrument is a magnificent Paramount ME/Celestron 14 telescope, housed in an adapted run-off plastic shed (off-the shelf from B&Q). The telescope is fully automated, allowing Martin to observe from the comfort of his study! He also has a 250 mm F6 reflector in another shed, or "dog kennel" as he describes it and various other telescopes dotted about his garden. Martin and his father have built some ingenious housing arrangements for his instruments. Martin explained that arachnids getting inside the equipment are a major bugbear, and moreover, he is convinced that the local spider population is mutating into giant form and that some have the physical capability of running off with eyepieces! We spent a fascinating half hour looking over the telescopes before adjourning for a most pleasant lunch at a nearby restaurant.
Following lunch, before driving Allan back to Oxford, returning once more to local astronomical history we visited Cockfield's nearby church to see the bricked up remains of a transit instrument slot in the church tower. During the 18th century the Rev William Ludlam (1716-1788) had the living at Cockfield and adapted the top of the tower for his own astronomical observations. With a minute amount of assistance from me, Martin had researched Ludlam's Observatory and had a paper published on the subject in JBAA June 20064.
During the long drive back to Oxford, Allan reflected on our mini historical tour of southern Suffolk and the fascinating juxtaposition of old and new that we had observed. It is self evident that he enjoys his trips to OASI and is looking forward to his next sojourn to what he refers to as "Airy Country".
Some of the audience at the lecture. Allan at centre front. (John Wainwright.)
OASI's 40th birthday cake. (Ken Goward.)
Allan and Roy cut the cake, held carefully by Pete Richards. (Ken Goward.)
Donati's Comet over Cambridge Observatory5, 1858.
Allan and Ken outside the Athenaeum. (Martin Mobberley.)
Allan on the narrow access stairs to the observatory. (Martin Mobberley.)
Martin, Allan and Ken in front of Martin's Celestron 14 SCT in its run-off shed. (Martin Mobberley.)
||Previously, UK Government funding had only been available for the Royal Observatory at Greenwich (established in 1675) via the Board of Admiralty. The object of work at Greenwich was to chart the night sky accurately in order to aid navigation at sea.
||JBAA Vol 115, 5, pp.251-261, 2005, "The Bury St Edmunds Athenaeum Observatory".
||For more details on Martin's observatory, see his web site.
||JBAA Vol 116, 3, pp.119-126, 2006, "The Rev William Ludlam and the Cockfield Tower Observatory".
||The comet is pictured over the dome of the Northumberland Refractor at Cambridge, on 11 October 1858. The image is from the Illustrated London News of 23 October 1858.
Ken Goward, FRAS
BAA-OASI Back To Basics Workshop, 20 January 2007
We held the first of our 40th anniversary events, the BAA-OASI Back to Basics Workshop, at the Methodist Church Halls in Ipswich town centre on Saturday 20th January 2007. Although a disappointingly low number of visitors attended the event, those who did so judged it to be a great success.
For OASI the event really began on the preceding evening, when a small group of volunteers transformed the church and side rooms into a credible conference and exhibition venue in the space of a couple of hours. One particularly astronomical touch was to arrange the hymn number boards on either side of the altar to display well-known four figure NGC numbers rather than the familiar numbers of the hymnal; the gesture was successful, as at least one visitor commented on the seemingly large number of hymns that must be contained within the Methodist hymn book!
On the morning of the event, we had a small publicity coup when OASI Chairman Ken Goward was invited to speak live on BBC Radio Suffolk during the Rachael Sloane Saturday Show. Each week Rachael invites listeners to phone in and enter a draw for which the prize is attendance at a mystery activity or event - the prize on this occasion being two places at the BAA-OASI Workshop followed by a meal at the Shepherd & Dog Carvery, courtesy of OASI, and thereafter an evening visit to Orwell Park Observatory to tour the night sky. Rachael selected the winner at random, and Ken revealed the prize to her. She expressed great delight on air at her good fortune. However, shortly after the broadcast it transpired that she had a dinner party planned for the evening and therefore wasn't able to accept her prize. A few quick telephone calls by the BBC Suffolk people and the prize was awarded to the next in line contestant, "Colin of Mendlesham". Colin and his partner thoroughly enjoyed the day and the evening visit to Orwell Park as was evident from the fulsome praise that he heaped upon OASI when interviewed by Rachael about his experience on the following week's show.
By the time Ken returned from the offices of Radio Suffolk to the Methodist Halls, things were in full swing: traders were preparing their stalls, BAA speakers were arriving and a small group of OASI volunteers under the instructions of Dee McLeavey was preparing a splendid buffet luncheon for the speakers and exhibitors, whilst Pete Richards and Nikky Gillard were preparing the first brew of tea and coffee refreshments that they would serve the whole day through. In the main lecture hall Paul Whiting was preparing a very interesting display promoting OASI and its activities, alongside displays by the BAA Radio Astronomy Group and the Society for the History of Astronomy.
At 10:20am, Dr Richard Miles, BAA President, officially opened the day. The programme was as follows.
- 10:00 - 10:20 Registration and tea/coffee
- 10:20 - 10:30 Official Welcome, Dr Richard Miles (BAA President)
- 10:30 - 11:15 Solar Observing, Peter Meadows
- 11:15 - 12:00 Variable Stars, Guy Hurst
- 12:00 - 12:45 Radio Astronomy, Laurence Newell
- 12:45 - 14:00 Lunch and solar observing outside the Hall
- 14:00 - 14:45 Equipment Demonstration and Advice, Bob Marriott
- 14:45 - 15:30 Imaging, Martin Taylor
- 15:30 - 16:00 Tea/coffee
- 16:00 - 16:45 Simple Deep Sky Observing, Dr Stewart Moore
- 16:45 - 17:30 Closing Address, Dr Richard Miles
Each speaker gave a most interesting and informative presentation, reflecting the long tradition of excellence of the BAA. Members of the audience, whatever their level of experience and knowledge, gained much useful information. At lunchtime, the Sun even cooperated and many people enjoyed good views of the solar disk through instruments set out in the car park. The instruments included the Hydrogen-alpha telescope belonging to OASI member Bill Barton, which revealed a solar prominence.
During his closing address the BAA President, Dr Richard Miles, thanked OASI for our efforts and presented Ken Goward by way of thanks with a book for the OASI library. Thereafter several members of the BAA and OASI enjoyed a meal at the Shepherd & Dog Carvery before going to Orwell Park Observatory for a session with the Tomline Refractor on a crystal clear evening (to make a welcome change!) Those present enjoyed good views of several deep sky objects. Several members of OASI undertook the Orion star count with "eagle eyed" Martin Cook managing to count 29 or 30 stars with the naked eye, when fully dark adapted, within the rectangle formed by Betelgeuse, Bellatrix, Rigel and Saiph. (The BAA organised the Orion star count as a project open to all providing a means of estimating the effect of light pollution on the limiting magnitude visible across the land.)
The event was a great success, and it provided the best possible start for our 40th anniversary year. (To top it all, during Saturday afternoon Ipswich Town FC even won a match at Portman Road, the reverberating full time cheer raising the hearts of all who heard it!) Finally, thanks are of course due to the wonderful support and efforts of our volunteer helpers and those of the BAA, without whom the event could not have been staged. Special mention must also be made at this juncture of Dee - who certainly has a bright future in the catering trade!
After the event, Hazel Collett, Meeting Secretary of the BAA and Event Organiser, wrote a letter of thanks to OASI Chairman, Ken Goward as follows:
I am writing to thank you and all the members of Orwell AS for all the help both before and during the event on Saturday which made our Back to Basics workshop go so well. I am fully aware of the amount of work that this entailed so I much appreciate this.
We had 53 participants in total and they were all impressed with the venue and the refreshments, but more importantly there were numerous comments about how friendly and helpful all the Orwell folk were during the day and especially during the practical sessions.
I hope the book we presented to you will be a reminder of a wonderful day and mark the start of your 40th Year celebrations.
Thank you again for providing all the refreshments for the delegates as well as the wonderful lunch for the speakers and organisers.
Please can you also pass on my thanks to those folk providing the AV support and for bringing the back-up equipment.
Finally, will you please express our sincere thanks to Roy for bringing the telescopes along even though Bob Marriott did not actually use them on the day.
Thank you once again for helping to make Saturday a great success.
Delegates enjoying a chinwag and welcome refreshments. (Pete Richards.)
More conversation and refreshments. (Roy Gooding.)
Dee McLeavey and her "volunteer" caterers. (Roy Gooding.)
Solar observing in the car park at lunchtime. (Roy Gooding.)
Ken Goward, FRAS
Celebration Of The 50th Anniversary Of The Society For Popular Astronomy, 04 October 2003
The Society For Popular Astronomy (SPA) celebrated its 50th anniversary in 2003. In late 2002, the SPA began making enquiries of UK astronomical societies seeking a partner to host a joint meeting to celebrate the event. OASI Secretary Roy Gooding volunteered to work with the SPA to organise a joint celebration. Subsequently, somewhat bizarrely, the SPA took minimal involvement in the project! However, Roy succeeded in organising a first class astronomy meeting to mark the anniversary. The meeting was held at Mary Magdalene Church Hall, Highfield Approach, Ipswich. The speakers were:
- Martin Mobberley, Imaging Comets.
- Martin Lunn, Pre-Telescope Astronomy.
- Neil Morley, Update On The OASI Millennium Telescope.
- Paul Whiting, Report On Observation of Solar Eclipse 04 December 2002 From Australia.
- Nigel Evans, Report On Observation of Solar Eclipse 04 December 2002 From Australia.
The OASI Millennium Telescope was on display during the meeting (prior to completion of its main mirror). The event was a spectacular success and did much to boost public interest in astronomy in and around Ipswich.
The following photographs (all by Roy Gooding) record something of the event.
Setting up for the meeting. The OASI Millennium Telescope (with dummy mirror) is in centre image.
Perusing books on the trade stands.
Ken Goward, OASI Chairman, opens proceedings. (Roy Gooding.)
The audience during Ken Goward's opening address. (Roy Gooding.)
Presidential Lecture, 07 March 2003
Oh what a night! Opening words from some largely forgotten pop song by some even more forgettable pop group - but most apt to describe the first OASI Presidential Lecture by Dr Allan Chapman on Friday 07 March 2003.
Held in the hall of Orwell Park School, Dr Chapman's long awaited lecture on The Victorian Amateur Tradition drew a large audience from members of OASI along with staff from Orwell Park School, members of Clacton & District Astronomical Society and other invited guests including descendants (great-great granddaughters Nicole and Kristian) of the 7th Astronomer Royal, Sir George Biddell Airy KCB. For the best part of two hours Allan held the audience spellbound as he painted a comprehensive picture of Victorian astronomy, of the nature of amateur status in the era and of the colourful and sometimes dubious characters from all walks of life indulging in the master science. It was obvious to all that Allan has an absolute mastery of his subject and at the conclusion of his talk he was given an extended and well-deserved round of applause from an appreciative audience.
Following his talk, Allan presented OASI's former chairman, David Payne, with an engraved pewter tankard to commemorate his extraordinary 21-year term of office. Orwell Park School then generously laid on a splendid cheese and wine reception - along with a large pot of tea for Allan, whose capacity for the fluid is the stuff of legends! The reception was enjoyed by all.
Afterwards, Allan and the Airy family were invited to the Observatory and treated to a tour of the night sky by Martin Cook, David Payne and Roy Gooding. Jupiter and Saturn were the main targets, but the Whirlpool Galaxy (M51) also provided a fine show for our guests. Allan's observing ability was self-evident and the Airy family, who had never previously looked through an astronomical telescope, were enthralled by the views. So much so, that it was almost midnight before we made our way back downstairs!
The following morning, at the kind invitation of Andrew Auster, Headmaster of Orwell Park, our guests returned to the school and were given a guided tour of the clock tower by Mrs Auster and Martin Cook. To round off the morning before catching their trains home they were taken to Playford for a visit to St Mary's Church to see the Airy family monuments and pay their respects at the Airy and Biddell graves in that most serene of churchyards.
We are grateful to our Honorary President for taking time from his very busy schedule to honour us with a lecture and without doubt all who attended can't wait for his return. We are also most grateful to Orwell Park School for their exceptional hospitality throughout Allan's visit. Here's looking forward to another Presidential lecture - 18/24 months from now!
Allan Chapman makes the presentation to David Payne. (Ken Goward.)
Allan Chapman at the top of the Clock Tower, with the Observatory in the background. (Ken Goward.)
Dr Chapman's long awaited TV series Gods in the Sky is almost ready and likely to be transmitted on Channel 4 during summer 2003. So pleased are the programme makers with the series that initial talks are taking place with a view to filming a follow-on series. Allan will also be appearing with Sir Patrick Moore in the May 2003 Sky at Night - on the subject of historical transits of Mercury.
Ken Goward, FRAS
Hubble's Constant, 12 July 1992
On 12 July 1992 at the Friend's Meeting House, Fonnereau Road, Ipswich, Dr David Dewhirst from the Institute of Astronomy at Cambridge presented a fascinating talk to OASI, with the title Hubble's Constant.
Edwin Hubble (1889-1953) discovered the law named after him in 1929 based on observations obtained with the Mount Wilson 2.5 m telescope. He measured the spectra of distant galaxies and discovered that nearly all exhibited absorption lines shifted towards the red. He interpreted this as a Doppler effect indicating that the galaxies were receding at high speed. He noticed that the fainter galaxies (presumed to be the most distant) had the greatest redshift and that, in fact, redshift was approximately proportional to distance. In symbols, the recessional velocity v and distance from Earth r are related by a constant H0, known as Hubble's Constant, as follows:
v = H0.r
with H0 usually expressed in units of km/second/megaparsec, v in km/s and r in megaparsecs.
It is generally accepted that the observed redshift of the galaxies is not, in fact, due to a Doppler shift as such, but rather to the expansion of space-time which carries everything in the universe along with it and causes the wavelengths of the photons emitted by the galaxies to increase.
Astronomers estimate the value of H0 by measuring the recessional velocities and distances of remote galaxies. It is easy to make a measurement of the redshift of a galaxy, however there can be significant problems in interpreting it. In order to validate Hubble's law over the full scale of the universe, astronomers study galaxies at very great distances. Unfortunately, distance measurements in astronomy are based on a hierarchy of increasingly inaccurate methods as a result of which they are very uncertain at large values. The effect of these uncertainties has been to produce two schools of thought on the value of Hubble's Constant - one finds the value of H0 to be in the range 45-60 km/s/Mpc, the other a larger value in the range 75-100 km/s/Mpc.
If the universe has been expanding at a constant rate since the Big Bang then its age is given simply by 1/H0. This quantity represents an upper limit on the age of the universe for standard cosmological models. In such models the effect of gravity is to slow expansion of the galaxies as time passes giving a larger value for H0 in the past corresponding to a younger universe. The maximum age of the universe corresponding to the above two estimates of the value of H0 are as follows:
H0 = 50 km/s/Mpc: max age 20 billion years.
H0 = 100 km/s/Mpc: max age 10 billion years.
David is now of the opinion that evidence is mounting to support the larger value of Hubble's Constant corresponding to a younger universe. He admits that this raises some important problems concerning our understanding of cosmology and astrophysics. One problem is that favoured models for stellar evolution give a computed age of the older globular clusters around our galaxy as 14 to 20 billion years and this seems to favour the smaller value for Hubble's constant. However the argument is by no means clear and major questions are outstanding about stellar evolution. For example, we still do not have a good explanation for the observed lack of neutrinos emitted by our Sun indicating some gap in our knowledge of stellar physics.
David's talk was stimulating and thought provoking and those who attended had a very interesting evening!
Asteroids, 16 February 1990
The lecture meeting of 16 February 1990 was our first for almost two years. The speaker was OASI member Neil Taylor (well-known for running evening classes on astronomy at Felixstowe for several years). Neil's topic was Asteroids. He had previously presented the lecture at our 21st annniversary celebrations in 1988; only a few members had been able to attend his presentation then, as most were busy managing the numerous events of the day.
Approximately 20 members attended. (This was a good attendance - at some past meetings the audience has numbered fewer than 10!) Neil started with an overview of the Solar System, then went on to discuss the discovery of the three outer planets, the Titius-Bode empirical law of planetary distance, and the discovery of the asteroids. The evening concluded with a discussion and Q&A session.
Halley's Comet From The Australian Outback, 13 March 1987
On 20 June 1986, Alan Smith and Roy Cheesman first presented a report of their Australian trip of April 1986. Unfortunately, less than a dozen people attended, a figure that was never explained, particularly in view of the large number of people who had expressed an interest in their exploits.
On 13 March 1987, they delivered a reprise, and this time, their efforts were amply rewarded, with the Collinson Room of the Friends' Meeting House packed with some 40-50 people (the largest audience for many years). Due to restrictions on the length of the meeting, Alan and Roy presented only a fraction of their collection of slides from the trip, together with a description of the locations and various anecdotes, many most amusing. The audience maintained rapt attention during the one and a half hours of the lecture, and at the end showed their appreciation of a most enjoyable evening.
Short Talks Evening, 13 February 1987
On Friday 13 February 1987 (unlucky for some!), members delivered short talks in the Collinson Room at the Friends Meeting House in Fonnereau Road. Unfortunately, the attendance at this very interesting meeting was poor, only ten people including the speakers.
Mike Harlow gave the first talk, on a Schmidt camera which he has constructed. He provided much technical detail, which he made readily comprehensible with the help of slides and diagrams. He also showed some of the equipment that he used to shape and polish the glass blanks used to form the mirror and corrector plate. Mike made it sound so easy, but I think that the practical aspects might be a little beyond me...!
Next, Roy Gooding showed and talked about slides of Comet Halley, some of which I hadn't seen before. However, the thing that caused most discussion was the slide projector, which resolutely refused to focus on the black and white slides and just kept winding the focus in and out.
David Payne should have been the third speaker, talking about eyepieces. But he had been in Scotland for work and was travelling home by plane and, unfortunately, it was late landing, and there was not even a meal on the flight. So he went straight home for some much-needed food and relaxation.
Halley's Comet From The Australian Outback, 20 June 1986
On Friday 20 June 1986 at the Friends' Meeting House, OASI's intrepid explorers Roy Cheesman and Alan Smith gave a presentation and slide show on their trip to the Australian outback to observe Halley's Comet.
Roy and Alan made the audience envious as they retold their exploits during the 3000 mile journey across the Australian continent. Many of the stories were hilarious. One of the funniest was the encounter with an Australian-German opal miner at Coober Pedy mine. Roy and Alan had left the main party during the evening of their visit to the mines to find an isolated, pitch-dark area from which to photograph Halley's Comet without disturbance from people roaming with torches. Having found a suitably dark and deserted spot a good distance from any sign of civilisation they proceeded to set up their equipment and start photographing. Within minutes of getting thoroughly dark adapted there came a blinding light from an aperture that mysteriously appeared in the ground a few feet from where they were observing. This began to feel like part of Close Encounters of the Third Kind and sure enough from the hole in the ground emerged a small spindly creature who, oblivious to the two astronomers, proceeded to relieve himself! Upon turning round to re-enter his hole the creature saw Roy and Alan and challenged them in a strange language that turned out to be Australian with a German accent! Once Roy and Alan had explained to the creature who they were and what they were trying to do, the Australian-German miner said words to the effect: Oh! Good on yer, mate. I'll leave the light on so's yer can see what yer doing.
The story didn't finish there but you had to be at the presentation to enjoy the telling fully, and the recounting of many other exploits, all accompanied by nearly 200 excellent slides. It was a memorable evening and certainly was a journey of a lifetime for Roy and Alan. Although the lecture was excellent, for reasons unknown attendance was unexpectedly poor, with less than a dozen people in the audience. (The lecture was therefore repeated on 13 March 1987 for the benefit of those who missed it the first time round.)
Some of the slides shown at the presentation are below.
Alan at Siding Springs Observatory, 08 April 1986.
Patrick Moore at Siding Springs Observatory, 08 April 1986.
Partial solar eclipse, 09 April 1986, 06:00 UT.
Comet Halley photographed from the vicinity of Coober Pedy mine, 11 April 1986.
Woomera, 11 April 1986.
Henbury Meteor Crater, 15 April 1986.
Solar System Dynamics, 09 December 1983
On 09 December 1983 at the Friends' Meeting House, Neil Taylor presented a lecture to OASI on Solar System Dynamics. Unfortunately, only eight members of OASI attended, but they enjoyed a most interesting evening. Neil reviewed the role of gravity in the Solar System and the history of observations which culminated in Newton's universal law of gravitation. In the latter part of his talk, Neil recounted some research into the orbits of the moons of Jupiter that he carried out when working for his degree. His research led to some interesting possibilities, including the potential existence of a highly depleted belt of asteroids between the orbits of Jupiter and Saturn.
Interstellar And Intergalactic Matter, 23 March 1979
On 23 March 1979 at the Friends' Meeting House, Iain Nicholson presented a lecture to OASI on Intergalactic and Interstellar Matter. He told a large attendance, including some folk from Colchester, how it appeared that instead of the Universe expanding for over and getting generally less and less dense (so that the distances between individual stars would grow without limit in the distant future) the boredom may ultimately be alleviated by a reversal of the expansion - such that that the edge or shell of the Universe may not be able to escape from the centre. This would bring the entire Universe crashing back together again at some distant future epoch.
One key point which Iain brought out was that life on Earth may have originated in outer space, not on the planet. All the materials and situations are present in space, between the stars and galaxies, for life to evolve, possibly doing so several times over!
The audience enjoyed an excellent time and much food for thought - not too technical. There were some hitches: the slides were the wrong way around and the No Smoking notice caused a constriction in the air-flow cooling the overhead projector, which resulted in the latter emitting some smoke! Iain commented that there is enough of various types of obscuring, but otherwise useful, matter in and around the galaxies not to need it at lectures as well. In any case the hitches did not detract from a very enjoyable lecture.
Members Short Talks Evening, 15 December 1978
On 15 December 1978, we were treated to an example of what members of OASI can do when called upon! Charles Radley gave an account of the history of Orwell Park Observatory, David Payne informed us about cosmology and Colin Munford provided much detail about variable stars.
After a coffee break our Chairman, Roy Cheesman, demonstrated his home-made planetarium, making us feel for a while that we had been transported to the professional facility in London! The show was in a room with squared-up walls and ceiling; one day, we will have to persuade Roy to give a show in the Observatory dome, which the equipment was really designed for. The main projector consists of a large ball with - seemingly - countless holes, slowly turning, with a small light at its centre. A tape-recorded commentary and changes of scene provided by another projector helped to transport us far away in a very short space of time. We were all very sorry when the Sun at last came out after a great demonstration.
Sun Worshipping, 17 November 1978
Aspiring to be a solar observer, I found Peter Laycock's lecture Sun Worshipping (17 November 1978) to be most interesting. Peter encouraged those of us who routinely put away our telescopes for the summer because of the short, twilight nights, instead to leave them accessible for use on the Sun. The Sun offers us a star to study at very close range and solar astronomy offers a continually changing pattern of phenomena of which amateurs' observations can be of great value, especially during generally bad weather when one may be fortunate enough to record an event which is of short duration but considerable significance.
Although it is sometimes possible to observe the Sun without a telescope, the most common approach is with a telescope and projection screen or other apparatus such as a spectroscope with a transmission grating (at least 600 lines per mm!) and an open slit for viewing prominences. Peter described a prominence telescope with hydrogen-alpha filter. He uses a coelestat, which he constructed himself, and which can feed the Sun's rays into a number of instruments in his observatory. He described the technicalities of oscillating slits and variable blanking cones during a question-and-answer discussion with the audience.
Those present at the lecture much enjoyed it and appreciated the work that Peter had put into constructing his apparatus, some of which he displayed.
NB: Always adopt appropriate safety precautions when observing the Sun.
Handout from the talk.
The Sun, 12 March 1976
Mr P Gill, FRAS gave an illustrated lecture on The Sun on 12 March 1976. Approximately 40 people attended, and although Mr Gill does not give many lectures, this one proved to be very enlightening for those interested in observing the Sun.
Geology Of The Solar System, 05 December 1975
Text of the presentation by Robert Markham (with additional material) to the joint OASI / Ipswich Geological Group meeting on 05 December 1975.
Geology is the study of the composition and origin of rocks, and of the history of the Earth as told by the layers of rocks of which it is composed. Space probes are now adding to our knowledge of geological processes operating in different physical environments; however difficulties may arise in interpretation of data from other worlds. In the Solar System, bodies of predominantly geological interest are of "high" density (over three times that of water) and rocky: Mercury, Venus, Earth, the Moon, Mars, Io and Europa. In contrast, "low" density bodies (density less than 2.5 times that of water) may have a large percentage of ice(s): these are Jupiter, Saturn, Uranus, Neptune, and most of the satellites of these planets.
The Earth has a radius of 6378 km, a mean density of 5500 kg/m3, and a thin rocky crust on top of a very hot interior. It has large quantities of surface water (Earth is the only planet with oceans of water), a nitrogen and oxygen atmosphere and abundant living organisms. The planet has, at the present time, polar ice caps. Stratigraphers, scientists who decipher the events preserved in the sequence of rock strata, study the formation of this environment during geological time.
Seismological measurements of the Earth suggest that it has a solid core of nickel-iron alloy, surrounded by a similar alloy in a molten state (where the Earth's magnetic field is thought to originate) with a mantle of silicate rocks essentially comprising the minerals olivine and pyroxene. The crust, generally 10 - 50 km thick, forms the outer rigid shell of the planet. There is evidence of major horizontal movement of great crustal plates resulting from convection currents generated by radioactive heat within the mantle. In some locations, the plates collide and push up chains of "fold" mountains, and in other locations they pull apart along rift zones such as the mid-Atlantic and East African rifts.
Igneous rocks solidify from hot molten lava-like material within the Earth; the constituent minerals of such rocks form an interlocking mass of crystals. Sedimentary rocks are formed of fragments and particles eroded from the surface of the Earth by disintegration and weathering, followed by transportation and deposition (generally in water); they may be cemented together by minerals precipitated from solution. Metamorphic rocks are formed by the alteration of other rocks as the result of intense pressure and heat within the crust forming new minerals and structures. The oldest rocks known on Earth are about 3,700 million years old, dated by the method of radioactive decay.
Low-lying areas of continental crust are subjected to continuous, slow, up and down movement leading to marine inundation (and sedimentation in shallow seas) and uplift to form new land. In such areas, fossiles may be found; these are the remains and traces of once-living animals and plants, and show the evolution of various groups of organisms.
Scientists have identified meteorite impact craters on Earth. They are sometimes associated with fragments of meteorites. However with most such craters there is no associated meteoritic material, and then the formation of the feature by impact is inferred from its shape, shattered and broken rock at the bottom of the crater, and the presence of minerals formed only under extremely high pressures, such as coesite (a form of quartz). However, with some craters there is no very convincing evidence that they were caused by a falling meteorite. A number of "fossil" craters are known, e.g. on the Canadian Shield, which have been preserved by burial under sediments.
The use of geological information to date the suggested "capture" by the Earth of the Moon has led to some highly speculative ideas. Some scientists place the capture event at the time of the major break (at most localities) in the geological succession at the Pre-Cambrian / Cambrian boundary nearly 600 million years ago; others place it at 3,000+ million years ago, based on growth patterns in stromatolites (possible evidence of lunar-influenced tides on the development of fossil plants).
The appearance of green (photosynthesising) plants on Earth in Pre-Cambrian times suggests that the Sun has been shining for a very long time. The apparent correlation of the cyclic nature of annual growth rings in trees with the sunspot cycle (including the virtual absence of both cycles in the second half of the seventeenth century) suggests a method of studying the Sun's activity in the geological past by means of fossil trees.
Meteorites are extraterrestrial material. They are different to rocks on both the Earth and the Moon, and have fallen to the Earth's surface from space. Spectral studies show that they are similar to the asteroids. They are of three main types:
- "Irons" (siderites): metallic composition, often 90% iron, about 8% nickel with traces of other elements. There are several sub-divisions, e.g. the octahedrite sub-division containing the minerals kamacite and taenite.
- "Stony-irons" (siderolites): silicate mineral(s) associated with iron. There are several sub-divisions, e.g. the pallasite sub-division which has nickel-iron alloy enclosing olivine.
- "Stones" (aerolites): mainly silicate minerals. Most belong to the group called chondrites (usually containing spherical particles known as chondrules) - they total about 85% of all meteorites and are subdivided according to the minerals that they contain.
Radioactive dating shows that most meteoritic material is about 4,600 million years old. Mineralogy of meteorites gives clues to the temperature and pressure at their formation, palaeomagnetic evidence gives data on primordial magnetic fields, measurement of abundance of certain elements may give clues to the temperature of the early Sun, and tracks left by energetic sub-atomic particles give indications of the post-formation history of the meteorite.
One of the groups of chondrites (the carbonaceous chondrites) contains carbon compounds including amino acids; there is dispute as to whether this is a terrestrial contaminant or indigenous, and if the latter whether or not it is of biological origin. Some stones, e.g. the Orgeuil Carbonaceous Chondrite contain organised elements which some scientists have suggested may possibly be microfossils; again there are similar disputes as with the amino acids.
Tektites are pieces of glass of disputed origin (terrestrial or extraterrestrial or both), dated between 0.3 and 30 million years old. Some scientists have suggested a correlation between the Moldavite tektites in Czechoslovakia and the 14.8 million year old Ries crater in Germany. Some scientists have suggested a link between some Far East tektites and the lunar crater Tycho.
The diameter of the Moon is 3476 km, about one quarter that of the Earth. It has a density of about 3300 kg/m3, approximately two thirds that of the Earth. The Moon has no atmosphere, no water and no life. On the Moon, erosion has not destroyed the record of past events - this confirms the absence of an atmosphere and water in the past.
There are two main surface areas on the Moon:
- Uplands or highlands. These are the light-coloured areas of the Moon; they are rugged and contain craters in profusion.
- Maria or seas. These are the dark areas, low-lying and relatively smooth, filled with deposits. There are two main types: the first is nearly circular and surrounded by nearly circular mountain arcs, e.g. Mare Imbrium. The second has an irregular outline with no bordering mountain walls, e.g. Mare Tranquillitatis. Their origin, meteoritic or volcanic, is still uncertain and so too is the nature of their infill (lava or ejecta). The maria consist of a granular regolith (thin deposit of pulverised rock debris) overlying what is probably volcanic lava but which may possibly be sheets of ejecta. There are unflooded basins (lacking mare material) on the far side of the Moon.
The Apollo missions returned three main types of surface material from the Moon:
- fine powdery material or "soil",
- crystalline igneous rocks,
- breccias (rocks consisting of broken fragments of pre-existing rocks welded together by impacts).
The lunar regolith or "soil" consists of minute rock fragments, mineral fragments, glass fragments and glass spheres, all very small in size. It was formed over a long period of time by meteorite and micro-meteorite impacts which have broken and melted the surface rock. Large rocks are scattered around in the soil and on the surface; they are common around the rims of recently formed craters. The regolith extends to a depth of a few metres.
Basalt, a crystalline rock, thought to originate on the Moon as molten lava (by analogy with properties of igneous rocks on Earth) is found in the maria. The maria basalts are composed of feldspar, pyroxene, ilmenite (iron titanium oxide) and smaller quantities of olivine.
Compared to the Earth, the Moon is poorer in volatile elements such as sodium, potassium and phosphorus but richer in refractory (high melting point) elements such as titanium and uranium; the latter are not concentrated as on Earth because of the lack of volatiles.
There is some breccia on the maria, produced by meteoritic impact breaking up rock and welding together the fragments by compression (shock metamorphism) or with the production of molten material.
The highlands of the Moon are formed mainly of breccia. They are cratered by numerous impacts. They are richer in aluminium (and therefore lighter) than the mare basalts. They are mostly composed of anorthositic gabbro, once molten, now crystalline. Anorthositic rocks are the most abundant lunar rocks thanks to the great quantities of the plagioclase feldspar CaAl2Si208. Some are composed of basalt, known as KREEP basalt because it is rich in potassium (K), rare Earth elements (REE) and phosphorus (P), formed by remelting.
Much work on lunar stratigraphy has been carried out by the United States Geological Survey. This work, combined with radioactive dating, provides the broad outline of lunar history. Relative ages are established by normal stratigraphic principles of cross-cutting relationships and superposition. The mountain terrain in the oldest part of the Moon formed in pre-maria epochs. The highland breccias, the oldest-known Moon rocks, are approximately 4000 million years old and formed at a time of intense cratering which produced the cratered highlands seen today. The anorthositic gabbro and KREEP basalt now forming the breccias would have originally crystallised at a time prior to its breaking up (brecciation). The maria appear to have formed about the time of the intense bombardment, and between 3900 million and 3200 million years ago were filled by basaltic lava, forming the maria rocks. (The oldest rocks known on Earth were formed when the lunar basins were being infilled.) A much lower crater density shows that the rate of cratering was very much less after the formation of these lava plains, and indeed the last 3,200 million years of the history of the Moon (post-maria time) show a low intensity bombardment producing occasional craters and meteoritic weathering of the surface.
Measures of changes produced by cosmic rays on rock gives a guide to the ages of post-maria craters: Copernicus is about 850 million years old, Camelot about 90 million years old and South Ray crater about 2 million years old. Ages of other craters can be estimated based on the freshness of their appearance compared with those of dated craters. Age relationships between craters are clear where one crater overlaps another directly. Otherwise, age relationships are determined by relative degrees of degradation (whether features are fresh and sharp or worn) as the steady bombardment by small meteoritic impacts breaks down original features. However, secondary ("splash") impacts can also break down original features and thus in some cases the degree of degradation of an older crater can depend on its proximity to another large fresh crater. Ejecta from the most recent impact basins has blanketed much of the earlier lunar surface.
No areas of solid rock have been found on the Moon; all sampled rocks have been separate rocks strewn around the surface and usually partly embedded in the dusty soil. This means that the crystalline rocks did not form where they were found. The basalts are usually interpreted as pieces of lava flow derived from melting of part of the lunar crust; it is thought that melting was caused by meteoritic impact, and that the impact also hurled rocks to their present positions. However, some scientists have suggested that the surface rocks are purely the result of "infall" (accumulation of meteorites) rather than of melting on the Moon; Moon rocks are unlike modern meteoritic materials but meteors may have had a generally different composition at the time that the Moon was forming.
Stratification has been observed on the Moon but it is not yet known whether it is due to lava flows or simply to the compaction of the powdery dust.
The origin (impact or/and volcanic) of the craters on the Moon is uncertain but evidence, though not conclusive, suggests that many large ray craters, e.g. Copernicus, are of impact origin. Large craters are generally circular structures with (when fresh) radiating swarms of small craters and ejecta; the small (secondary) craters are generally thought to have been formed by missiles ejected from the primary crater during its excavation. The bright ray systems have been interpreted as "splash" features. Terrace features inside some craters may be due to slumped blocks.
There is some evidence of volcanic activity on the Moon. Some irregular-shaped domes appear to be of volcanic origin. Possible lava outpourings may have come from vents in the maria, but molten rocks may have been generated by impact. Flow patterns of material on the maria are usually interpreted as volcanic lava but may be flows of other material (regolith?)
The major linear features of tectonic origin ("internal upheavals") so characteristic of Earth's surface are absent on the Moon; there are no signs of contortions in any of the ring shaped structures on the very ancient lunar surface. There are some smaller linear features such as the Straight Wall Fault, about 75 km long, in Mare Nubium. Some sinuous rilles may be collapsed "lava tubes" (formed by lava rivers flowing beneath a consolidated crust of lava).
"Moonquakes" originate at a very great depth (by contrast, most Earthquakes originate at shallow depths, less than 60 km). Seismic readings show the immediate subsurface structure of the Moon to be different from that of the Earth, and interpretation of bedrock as volcanic lava must take this into account.
The Moon has a negligible general magnetic field; any local crustal magnetic fields may be residual.
Mercury has a diameter of 4878 km, about two-fifths that of the Earth. It has a density of 5400 kg/m3, comparable to that of the Earth, suggesting a large metallic core. The planet has a magnetic field, possibly a remnant from an earlier phase of its history. The exterior of the planet is similar to the Moon, with a cratered surface and no atmosphere. The temperature at the surface rises to over 400°C.
Most of our knowledge of Mercury comes from observations by Mariner fly-by spacecraft; however, they imaged less than half of the total surface area. The Mariners showed two broad types of terrain:
- densely cratered terrain with large craters. This terrain resembles the highlands of the Moon.
- relatively lightly cratered plains similar to lunar maria, and possibly composed of volcanic material; they overlie the cratered surface.
The highlands of Mercury are similar in appearance to those of the Moon, with close-packed large basins and craters with superposed smaller craters. The craters are probably impact craters; this conclusion is based on the same criteria and arguments used in connection with lunar craters. However, there are differences between fresh craters on Mercury and on the Moon. Material ejected from primary impact craters on Mercury covers a less extensive area than on the Moon, and secondary impact craters are much closer to their primary craters; these effects are due to the greater gravity of Mercury.
The plains are relatively smooth areas, younger than most of the heavily cratered terrain. They are probably of volcanic (lava) origin rather than sheets of ejecta (as the plains material is not associated solely with large craters).
The Caloris Basin, 1300 km in diameter, is probably an impact basin comparable to the Imbrium Basin on the Moon. It is surrounded by a rim of mountains and the floor is filled with smooth plains material; the floor shows a fracture pattern of ridges and cracks implying post-emplacement movement in response to stresses.
If the craters of Mercury are 3-4 thousand million years old, their shapes show that there has been no crustal plate movement like that on Earth. Lack of surface erosion rules out any atmosphere in the past. Subsurface temperatures in equatorial regions are above the freezing point of water but no evidence has so far been observed of chemical weathering conceivably associated with the occasional release of subsurface water. It appears that the present surface of Mercury, like that of the Moon, was formed early in its history and has changed little since.
Venus is approximately the same size and density as the Earth and it is possible that its internal structure is similar too; if so, the apparent absence of a magnetic field might be explained because the planet rotates very slowly. Venus has an atmosphere, primarily carbon dioxide, with a surface pressure about ninety times that at the surface of the Earth. The surface temperature is over 450°C, the clouds seeming to "trap" sunlight to maintain this temperature.
No surface features have been viewed from space because of the cloudy atmosphere. However, radar mapping distinguishes terrain as rough or smooth, and as high or low, and indicates that Venus generally appears to be much flatter than the Moon, Mercury, Mars and Earth. Surface features, for example mountains, are often large in extent but with a small range of heights and depths; there are few features more than 1.5 km high. A few large circular crater-like forms are known; one large "crater" just north of Venus' equator is about 150 km in diameter but only about 0.5 km high at the rim, while its interior does not appear to be much below the level of the surrounding terrain. Meteoritic and volcanic origins have been suggested. The apparent scarcity of small craters, if of meteoritic origin, can be attributed to the planet having an atmosphere.
Venera landing spacecraft have photographed small parts of the surface of Venus. At one site there were numerous tabular, angular boulders, ranging in size from about 30 cm to 1 m across. The angular boulders are little eroded, indicating fairly recent breakage; "Venus-quakes" have been suggested as being responsible for shaping the blocks. At the other site, the landscape looked appreciably older, a plain with smoother rock outcrops. The composition of the surface is unknown, but observations of radioactivity indicate the presence of uranium, thorium and potassium, pointing to igneous rocks.
Reactions at the surface may include the action of wind, heat and rain. Observed motions of the atmosphere have been interpreted as high-speed winds extending over large areas, but winds at the surface seem to be very gentle. The high temperatures at the surface may possibly liberate gases from rocks, and may also deform low melting-point materials; information is not yet available on these points. It is thought that the Venusian clouds possibly contain sulphuric acid; any rain may therefore consist of hot acid, and the action of such a corrosive fluid may be responsible for the shallowness of surface features on the planet. Again, further information is not yet available.
It is obvious that any discussion of Venus involves a great deal of speculation at present; current and future work should greatly increase our knowledge of the planet. Any information about the geological history of Venue will be of great interest; conditions on the planet may have been very different in the past.
Asteroid 1685 Toro
Away from the main asteroid belt, the Apollo asteroids cross the orbit of Earth. The spectral characteristics of Apollo asteroid 1685 Toro match closely that of the L-type chondrite meteorites; could Toro possibly be composed of the same material as the latter? Many meteorites may be fragments of asteroids liberated during collisions with other asteroids.
Mars is about half the diameter of Earth. It has a density of 3900 kg/m3, and therefore its interior must be different from that of Earth. It has a tenuous atmosphere (surface pressure less than 2% the pressure at the surface of the Earth) rich in carbon dioxide. There is no liquid water on the planet because of low pressure and very cold conditions. Mars has no magnetic field.
Mariner spacecraft have shown that the southern hemisphere of the planet consists of densely cratered highlands, indicating a great age. There are several large multi-ringed impact craters on Mars; in the southern highlands, Hellas is nearly twice the size of the Imbrium basin on the Moon. Conversely, the northern hemisphere is low, smooth and sparsely cratered (resembling the lunar maria or plains), indicating comparative youth. There is evidence of geological activity, with volcanism, tectonism, and possibly fluvial processes. Thus Mars has analogies to both the Moon and the Earth.
Near the equator of Mars there are several gigantic mounds with craters on top, similar in appearance to terrestrial shield volcanoes. The largest, Olympus Mons, is over twice as large as the largest shield volcano on Earth. The summit features appear to be calderas (collapsed features once lava vents), and there are long, thin, lava-like flows and channels on the flanks. The flanks of these volcanic mountains are almost free of impact craters, implying comparative youth. Old volcanic features are also known.
The plains show many lobed scarps, resembling volcanic flow fronts, and indicating possible basaltic composition. Some areas have more craters than others, implying different periods of lava flooding.
The Valles Marineris complex is a great equatorial rift (fault) valley extending for 5000 km, in places 75 km wide and 6 km deep. There are diagonal subsidiary valleys, possibly of complex origin including fracturing, landslides, wind, and perhaps running water. There is evidence of fault blocks elsewhere, for example in the Tharsis plateau area.
No linear chain mountains (evidence of horizontal or crustal plate motions) have been identified.
Wind plays an important part in erosion and deposition of material on Mars. Scouring by wind may have faceted hills and may have etched the irregularly shaped, closed depressions in the south-polar regions. The scouring action of winds has modified and eroded craters, removed bright rays of ejecta, and created dust-streak tails trailing from some craters. Spacecraft have also photographed wind-sculpted sand-dune fields. Windblown dust is no doubt responsible for the seasonal changes of light and dark coloured material. The light-scattering properties of the surface of Mars are similar to those of the iron oxides limonite and geothite.
At the present time Mars has in its north and south polar regions small permanent ice-caps, apparently composed chiefly of water-ice, with seasonal ice-caps of carbon dioxide ice. Laminated terrain in the polar regions consists of numerous layers (each about 100 m thick) of sedimentary appearance, perhaps a mixture of dust and ice. The "cliff and bench" topography suggests varying resistance to erosion.
There is evidence of fluvial processes on Mars, with valleys which may have been formed by running water on the surface. There are meandering valleys, with highly sinuous courses, but of particular interest are the channels with many tributaries, which look as if they can only have been formed by rainfall, as the water needs to originate over a large area. Some valleys show braided terrain (networks of small channels) on their floors, another indication of fluvial action. Some channels are degraded and densely cratered, others appear "fresh" (with very few craters), implying widely differing ages.
The evidence of water action on Mars, where it cannot exist in liquid form at the present day because of the "glacial" conditions, implies the possibility of major climatic variations during Martian history. The duration of warmer climate and water erosion was short, as erosion has not destroyed pre-existing cratered surfaces. "Chaotic terrain", great masses of broken and tilted rocks, gives the impression of subsidence, perhaps due to the melting of subsurface ground ice.
The lack of free water and lack of atmospheric protection from radiation are not insuperable problems when considering the possibility of life existing on Mars at some stage during its history. It may well be worth looking for Martian fossils.
Martian history may be briefly summarised as follows:
- Formation of craters and basis of the cratered highlands.
- Formation of fault scarps and graben; breakup of northern crust.
- Formation of volcanic lava plains.
- Formation of major volcanic shields.
Postscript: Viking At Mars
Note: The above was written before the landing on Mars of the Viking spacecraft in 1976.
Viking 1 landed on Mars on 20 July 1976 in Chryse Planitia and Viking 2 landed on 03 September 1976 in Utopia Planitia. Images from both landing sites show rock boulders everywhere. Sand-dunes are present at the site of Viking 1; the rocks at the site of Viking 2 show vesicles similar to those of volcanic rocks on Earth.
The search for life on Mars is so far (as of September 1976) inconclusive; Martian soil material is very active but the processes are unknown. Material from under rocks (sheltered from ultra-violet radiation) is being analysed. Future missions may need to search for life in material in cracks in rocks rather than in loose material exposed on the surface.
Photographs from the Viking orbiters show the volcanoes and valleys in greater detail than previous missions. The North Polar Cap is water ice not carbon dioxide ice.
Phobos And Deimos
Phobos, the larger satellite of Mars, is a cratered, impact-eroded rocky chunk showing lineation features. Deimos, the smaller satellite, is also a cratered, impact-eroded rocky chunk similar, but without the lineation features.
Asteroids are minute in size (in comparison with the planets in the Solar System), have no significant gravitational field and so have no atmosphere. Scientists have spectro-photometrically examined many asteroids, and compared their spectra with those of powdered minerals. The most common (80%) asteroid surface material resembles that of carbonaceous chondrites; about 10% have a surface resembling laboratory spectra of stony-iron meteorites. Surfaces similar to nickel-iron have also been found.
Could the asteroids have once been part of one or more bodies which had segregated into a heavy metallic core with lighter surrounding material?
The Galilean Satellites of Jupiter
Io and Europa, the innermost Galilean satellites, each have densities over 3000 kg/m3, and therefore in terms of density appear similar to bodies of the type found in the inner Solar System. Some surface features are known. Io is about the same size as Earth's Moon, and has a tenuous atmosphere. It seems to be a reddish-brown colour, with darker reddish polar caps. It has been suggested that sulphur and sodium-rich evaporate salts may account for the colour. Europa is slightly smaller than the Moon, and has what appears to be snowy-looking polar caps, according to some accounts.
Ganymede and Callisto, the outermost Galilean satellites, are not dense enough to be composed solely of rock: they are likely to consist of a mix of ice and rock. It has been suggested that some darker features on the surfaces of Ganymede and Callisto may be due to rocky material embedded in an icy matrix. Ganymede is larger than the planet Mercury; it has definite dark and light surface areas and may have a thin atmosphere. Pioneer 10 captured images with a resolution of surface features of 400 m. Callisto is about the same size as Mercury, and darker than Ganymede.
Titan, the largest satellite of Saturn, is about the same size as Mercury. It is not dense enough to be composed solely of rock, but a hydrogen and methane atmosphere, deeper than that of Mars, makes it of particular interest. It has been suggested that the atmosphere may absorb sunlight, causing atmospheric heating and possibly resulting in the formation of complex organic molecules.
Comet Ikeya-Seki passed within 500,000 km of the Sun in 1965 and solar heating was enough to vaporise some of the stony matter in the head of the comet. Spectral analysis provided evidence of sodium, calcium, iron, nickel, chromium and other metallic elements.
Absolute (radioactive) dates are known only for the Earth and Moon. Comparative dating of events is sometimes possible if the objects involved (e.g. impacting objects such as meteorites) are extra-terrestrial and if they are from a common source and not of local origin. Extrapolation of our knowledge of the age of Moon rocks and cratered surfaces allows estimation of the age of surface features on Mercury and Mars.
Palaeoclimatology of Earth and Mars may be affected if the planets pass through dust clouds in space, perhaps giving rise to ice ages.
- Moss, A A, 1967, "Meteorites", British Museum (Natural History).
- Adams, P J, 1968, "The Moon", HMSO.
- Wilson, G, 1970, "Wrench Movements in the Aristarchus Region of the Moon", Proc. Geol. Assoc. London, vol. 81, pp. 595-608.
- Guest, J (Ed), 1971, "The Earth and its Satellite", London.
- Leet, L D & S Judson, 1971, "Physical Geology", (4th ed), Prentice-Hall, Inc.
- Sylvester-Bradley, P C, 1971, "Environmental Parameters for the Origin of Life", Proc. Geol. Assoc. London, vol. 82, pp. 87-135.
- Calder, N, 1972, "Restless Earth", BBC.
- Geological Museum (London), 1972, "The Story of the Earth", HMSO.
- "New Science in the Solar System", New Scientist Special Review, 1975.
- "The Solar System", Scientific American, September 1975.
- Turner, G, 1975, "Exploring the Moon", Sheffield Museum.
- Carr, M H, 1976, "The Volcanoes of Mars", Scientific American, January 1976, pp. 32-43.
- Sanders, R S, 1976, "The Geology and Geophysics of Mars", Endeavour, vol. xxxv, no. 124, pp 15-20, January 1976.
- Cruikshank, D, & D Robinson, 1976, "The Galilean Satellites of Jupiter", Scientific American, May 1976.
- "Soviets Reveal What They Found on Venus", New Scientist, 01 July 1976, p. 5.
Space Film Show, 31 October 1975
OASI's Space Film Show was the first of the Society's current series of events to be held in Ipswich town. The evening got off to an hilarious start with David Bearcroft, our projectionist for the evening due to indisposition of the regular incumbent, frantically reading the instruction book for the projector while the audience enjoyed the first film in slow motion with half-speed sound! Eventually, the appropriate switch was found to rectify matters. It is rumoured that David's cinematographic experience was inherited from his great, great grandfather, who used to light the candles at the Windmill in ye goode olde days. Despite the difficulties, the evening was very enjoyable.
The Amateur Astronomer, 26 April 1975
J Hedley Robinson, Director of the Mercury And Venus Section of the BAA, delivered a lecture on The Amateur Astronomer. The lecture followed a meeting of the Section earlier in the day at Orwell Park.
Report on the meeting and lecture in JBAA vol. 85, p. 450, 1975.
BAA Lunar Section Meeting And Lecture By Patrick Moore,
07 December 1974
The BAA Lunar Section held a provincial meeting at Orwell Park School on 07 December 1974. All who attended enjoyed a most enlightening afternoon.
Prior to the meeting, Patrick Moore, Commander Henry Hatfield and a few others inspected Orwell Park Observatory and the 26 cm refractor and were suitably impressed with what they saw. So much so, in fact, that Patrick jokingly asked Roy Cheesman if the telescope was for sale so that he could add it to his collection of instruments - but Commander Hatfield was determined to outbid Patrick if it ever came to market! Patrick and Commander Hatfield agreed that the 26 cm refractor was a fine instrument and that OASI was lucky to have the use of it.
The Lunar Section meeting started at 2.30pm and, after brief introductions, Patrick called for a volunteer to take notes. Unfortunately nobody present had high hopes of taking notes at 200 words per minute (!) so Patrick decided to take the notes himself with Commander Hatfield chairing the first half of the meeting. First to speak was the Chairman of OASI, Roy Cheesman, who welcomed the attendees on behalf of the Society. He followed the welcome with an account of how Colonel Tomline brought the Observatory and telescope into being, and how they had subsequently fallen into disrepair and suffered misuse until OASI restored them to their present grandeur. Mr Good, a member of the BAA, then presented a descriptive talk about outline maps of the lunar surface prepared from photographic material. The Mills Observatory at Dundee was using the maps for recording TLPs (Transient Lunar Phenomena). Next to speak was Mr Ellis, who addressed the CED (Crater Extinction Device), the unsuitability of the Kodak No 3 step tablet and the new neutral density filters now being employed for the work. He showed the new filters mounted on a revolving disk.
The meeting then adjourned for refreshments, served in the fine study next to the meeting hall. When it resumed, Roy Cheesman took the chair and invited Commander Hatfield to show slides of his observatory at stages during its construction and to describe in detail his telescope. Mr Reg Spry then gave the final talk, showing slides of various amateur observatories, including those built by Patrick Moore. Then, at 5.30pm, Patrick closed the meeting.
We later learned that one poor soul had been accidentally locked in the Observatory Tower all afternoon and missed the meeting. He had turned on the lights and opened the shutter of the dome to attract attention - fortunately someone noticed and he was freed. Charles Radley is prime suspect for inadvertently incarcerating the unfortunate individual!
On leaving Orwell Park School, Roy Cheesman and David Bearcroft took Patrick and the company for dinner at the Crown and Anchor Hotel. David remarked that he felt rather like an animal in the zoo, the way that the other diners kept looking at the OASI table! After a pleasant meal the company made a dash to Copleston School for the evening lecture.
On arriving at the school, private worries that any of the organisers might have harboured about low attendance were immediately dispelled as the hall was packed to capacity (530 people). Roy Cheesman provided an introduction and then Patrick delivered the evening lecture, entitled Into Space, in his own inimitable manner, holding the audience entranced for one hour and ten minutes. His humorous tales, accompanied by slides depicting Man's early attempts to venture into space amazed and captured the imagination of everybody present. After the lecture Patrick signed some 200 autographs, then we had coffee with Miss Beeson, headmistress of the school. At about 9.30pm we cursed the clouds which prevented a return visit to the Observatory to look through the telescope and Patrick started the long trek back to his home at Selsey.
Report on the meeting and lecture in JBAA vol. 85, pp. 265-7, 1975.
John Deans And David Bearcroft
JAS Provincial Meeting And lecture By Dr David Dewhirst,
04 May 1974
On 08 May 1973, the committee of OASI approved a proposal to host a meeting of the JAS (Junior Astronomical Society) in Ipswich on Saturday 04 May 1974. The original aim was to hold the meeting in the Friends Meeting House, Fonnereau Road but, in the event, influenced by the economic chaos induced by the oil shocks of 1973 and the miners' strike of 1974, OASI relied on the hospitality of Orwell Park School, which graciously opened a lecture hall and the canteen for the meeting.
Members of OASI were encouraged to help transport visitors to the meeting from Ipswich Railway Station to the School and, on the Sunday before the meeting, to attend a session from 9.00am until noon to clean the Observatory.
The meeting was held from 2.00pm to 3.30pm with principal speaker Dr David Dewhirst from the Institute of Astronomy, University of Cambridge, giving a lecture entitled Any More Planets Out There?, focussing on the possible existence of planets in addition to Pluto beyond the orbit of Neptune. Anyone arriving early was able to visit the Observatory, and was even promised a potential opportunity to observe with the Tomline Refractor a prominent sunspot group first seen by members of OASI in early April. The meeting was judged a great success.
Report on the lecture in Hermes (the journal of the JAS), 1974.
Charles Radley And Royston Cheesman
The Hertzsprung-Russell Diagram, 05 October 1973
On 05 October 1973, George Curtiss spoke to OASI on the Hertzsprung-Russell Diagram and the evolution of stars. Rather he spoke for half the time on this subject and spoke for the other half on many other things - but it was all very interesting! This was the first lecture meeting organised by OASI and it was a great success.