1125th General Monthly Meeting
How old is life on Earth?
Professor Malcolm Walter, Director of the Australian Centre for Astrobiology, Macquarie University.
Date: Wednesday, 12th May, 2004
Time: 7:00 for 7:15 pm
Venue: Lecture Room 3, Institute Building next to the Darlington Centre,
Sydney University.
Until about 10 years ago the palaeobiology of the earliest Earth was like studies of human evolution: a sparsely populated field characterised by minimal evidence and great public interest, a dangerous mix. A small number of practitioners dominated the field. All that has changed. The field has been galvanised by the entry of numerous new players and the application of new techniques. Much of this is caused by the exploration for life on Mars. The more we learn about Mars the more it seems reasonable to compare the early history of the two planets.
Professor Walter believes the palaeobiological history of Earth starts at 3.5 billion years ago and by then diverse microbial communities can be expected. The evidence comes from the Pilbara region of Western Australia and the Barberton Mountainland of South Africa. Despite continuing controversies that blur understanding, in recent years new mapping and new discoveries of probable fossils, particularly in the Pilbara, indicate the presence of complex microbial ecosystems. The evidence is not as clear as in younger rocks, but work in progress leads him to the view that within a few years convincing interpretations will be possible.
Enquiries: Prof. P.A. Williams
email: P.Williams@uws.edu.au
or phone the Society - details on Introduction page.
Professor Malcolm Walter has worked for 35 years on the geological evidence of early life on Earth, including the earliest convincing evidence of life. Since 1989 he has been funded by NASA in their "exobiology" and "astrobiology" programs, focusing on microbial life in high temperature ecosystems, and the search for life on Mars. He is a member of the Executive Council of NASA's Astrobiology Institute. During 1999 his book "The Search for Life on Mars" was published by Allen & Unwin. He has published more than 100 articles and several other books. He also works as an oil exploration consultant and a consultant to museums, and was curator of a special Centenary of Federation exhibition on space exploration (for the National Museum of Australia in Canberra, Museum Victoria, and elsewhere).
Report on the General Monthly Meeting
by Karina Kelly
Professor Walter gave the talk entitled: "How old is life on Earth?"
Professor Walter entertained and informed our audience on the fascinating subject of the age of life on Earth. He explained that the Pilbara in Western Australia was perhaps the best place in the world for gazing back 3.5 Billion years. The solar system is 4.5 Billion years old and the earliest crystals are 4.4 Billion years old. The oldest rocks on earth are 3.9 Billion years old but according to Walter it is not possible to get useable information from them. So the rocks of the Pilbara are the oldest. What this means is that it's not possible to see all the way back to when we think life began about 4 Billion years ago.
There is evidence that the earliest life on earth may have been thermophilic; needing much hotter temperatures - perhaps 80 degrees - to reproduce. For most of the Earth's history such primitive life forms were all that existed on the Earth. If life began 4 Billion years ago, then for 3.5 Billion, it consisted of such simple life-forms. They lived (and continue to live) up to 3 kilometres under the surface of the earth. Such life forms may be larger in volume than all the other life on Earth.
Only in the last 500 Million years have the larger animals that we are familiar with evolved so the process to get to our stage is long and slow. And what about Mars? Did life begin there and come to earth in an asteroid? It's just possible as Mars almost certainly had water, and life forms such as those deep in the earth's crust could survive inside a chunk of Martian rock. But whether life began here, on Mars or somewhere else is still open to argument.