ATNF Marsfield Lecture Theatre

Malcolm Walter

Going to Marble Bar to search for Life on Mars - Malcolm Walter colloquium

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. That has changed. The field has been galvanised by the entry of numerous new players and the application of new techniques. Much of this has been 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. However, much of the literature is arcane and some is polemical and must seem impenetrable to those not involved.

Proving the former existence of life at the microbial level is not easy unless there are well-preserved microfossils in a clear sedimentary context. There are hundreds of examples like this known from rocks younger than 2.5 billion years old, but none older. Despite this the record at 2.7-2.8 Ga is rich and not disputed. But from earlier times the record is much harder to decipher. There are many reasons for this. Foremost is the small number of sedimentary rock successions to work with, especially relatively unaltered ones.

As for evidence for life on Mars, there is no evidence that would convince any reasonable sceptic. But we may well know one way or the other within the next 20-30 years.