Fossils in Ancient Seabed may Shape the Search for Life on Mars

Microscopic fossils of primitive lifeforms found in what was a dried up part of the Mediterranean could help NASA scientists to determine where to look for fossils of primitive life on Mars.

The question whether there is or has been life on Mars has been hotly debated.  Certainly, there is evidence to indicate that in pre-history Mars was seismically active and perhaps it had a thicker atmosphere than it has today.  There is also plenty of evidence of water on the red planet and indeed despite the fact that what water on the planet is frozen solid, pictures taken from the Martian surface indicates geological features that may have been caused by rivers and flowing water.

The NASA Martian rover, known as Opportunity is currently traversing a relatively flat area of the planet called Meridiani Planum and this particular region of Mars is littered with rocks made from calcium sulphate (gypsum) the same rocky material in which scientists have found fossils of primitive life here on planet Earth.

The scientists said they are impressed by the unexpected discovery of 6-million-year-old fossils in rocks from a time when the Mediterranean Sea was known to have dried up completely.  The fossil life forms include organisms very much like those found at the bottom of Ocean food chains today, phytoplankton, diatoms and cyanobacteria.

Cyanobacteria (sometimes referred to as blue-green algae), evolved on Earth sometime during either the Archean Eon or the Proterozoic Eon, a period of time that covers the Earth from around 4 billion years ago to the beginning of the Cambrian Period.  Evidence of ancient microscopic life is extremely rare, especially in the earliest part of the Proterozoic Eon, (known as the Palaeoproterozoic), but some scientists have put forward fossil evidence to indicate that photosynthesising single-celled, micro-organisms without nucleii – prokaryotes evolved around 2.4 billion years ago.  It was the action of micro-organisms that radically changed the Earth’s atmosphere as they converted sunlight into food with oxygen as a bi-product.

A Comparison of Living and Fossil Bacteria

Picture Credit: Open University

The picture above shows six electron microscope studies of cyanobacteria, each with a scale in microns.  The pictures labelled (a), (c) and (e) are from cyanobacteria colonies found today in Mexico (stromatolites).  Pictures labelled (b), (d) and (f) are from rocks in the former Soviet Union, showing micro fossils of bacteria.  Picture (b) is approximately 950 million years old (Neoproterozoic), picture (d) has been dated to approximately 850 million years ago (Neoproterozoic) and picture (f) is the oldest specimen dating from the middle of the Proterozoic (Mesoproterozoic), approximately 1550 millon years ago.  The fossil bacteria resembles very closely the modern forms, indicating how little change has occurred in these organisms since they first evolved.  These relatively unchanging lifeforms that evolved in the in the Cryptozoic (the immense amount of time from the Earth’s formation to the first fossils of complex life forms), give credence to that often used phrase by palaeontologists that life on Earth was “on a long fuse to the Cambrian explosion”.

During a NASA phone briefing Wednesday, J. William Schopf, director of the Centre for the Study of Evolution and the Origin of Life at UCLA, said the fossil life forms found in the calcium sulphate rocks on Earth, present the intriguing possibility of the Martian rover finding similar fossil on the calcium sulphate rocks that are scattered across the part of Mars the rover is currently exploring.

Commenting on the discovery of micro-fossils in the gypsum rocks, Schopf stated that the scientists never expected to find signs of life.

“We all assumed there wouldn’t be anything like life there, and we were wrong.”

Gypsum is made of calcium sulfate, and Steven Squyres, chief scientist of the Mars Rover mission, noted that Opportunity’s six wheels are now carrying it across portions

Steven Squyres the chief scientist on the NASA Mars rover mission said that the rocks that Opportunity was now passing by would be “a fine target for intense investigation”.

Squyres is a member of a National Research Council task force weighing up future concepts for space missions that would seek evidence of life – past or present – on planets or other bodies in the solar system like the larger asteroids that orbit the sun between Mars and Jupiter.

After all, it is not just the planets such as Mars or a moon such as Europa that may harbour life, a recent study of a large asteroid in the main debris belt between Mars and Jupiter (24 Themis) has shown that asteroids too, may also contain water and have organic compounds.

To read more about the research on this asteroid: Scientist find Evidence of Water on an Asteroid

There are a number of missions currently being considered, each one with the aim of helping to prove that Earth is not alone in the solar system in terms of life, that once there was life, albeit primitive life, in other parts of our solar system.

One of particularly strong scientific interest would revive a 20-year-old plan to collect samples of Martian soil and return them to Earth for scientists to analyse in the best laboratories in the world.

Explaining how this mission would be carried out, Squyres stated that this mission would involve three spacecraft launched over six years.

The first would be a rover that would trundle across a selected Martian site, collect a variety of soil samples, and then “park in a nice, safe spot” to await a second spacecraft from Earth that would pick up the samples, blast off from the planet’s surface, and remain in Mars orbit until a third ship from Earth arrived to carry the priceless cargo back home.

The entire project, which Squyres described as “complex and hellishly difficult to complete,” has no price tag yet, but NASA planners say the concept is being studied as a potential joint venture by teams at the European Space Agency’s headquarters in Paris.
