Mars has been associated with extraterrestrial life for well over a century, although dreams of advanced beings, riding around in hovercraft, is unlikely. Still, we know of water ice hidden beneath the ruddy surface of Mars, within which we may find fossilized remains of life, or perhaps simple organisms still eking out an existence in the modern age.
Both NASA and the European Union (in partnership with Russia) will send spacecraft to Mars in the year 2020 to search for life, past or present, on the Red Planet. These robotic explorers are designed to examine volcanic igneous rocks which dominate the Martian landscape. However, here on Earth, fossils are nearly always found in sedimentary rocks, built up layer by layer over time. In preparation for the journey to Mars, researchers from Sweden are studying fossils within the structures of igneous rocks here on Earth, hoping to learn what to look for in Martian fossils.
“Earth’s fossil record is almost exclusively based on findings in sedimentary rocks, while igneous rocks have been considered barren of life, including a fossil record of past life. Since martian volcanic rocks will be targeted in the search for biosignatures, the lack of a terrestrial analog fossil record is an obvious impediment to the scientific aim of the mission,” researchers wrote in an article published in Frontiers in Earth Science.
This Place is a Real Dive
Far beneath the deepest ocean floor, fossils of ancient microbes, some of which date from 3.5 billion years ago, can still be found. Within this landscape where sunlight never falls, bacteria, fungi and other microscopic lifeforms consume igneous rock — and each other — as sustenance. These lifeforms fill cavities and fissures in rocks, where they fossilize upon death, occasionally forming fossils.
Deep drilling projects can bring these geological records of the earliest days of life on Earth to the surface, to be examined by geologists and other researchers piecing together the story of life on our planet. Fortunately for researchers studying life on Mars, the oceanic crust on Earth is similar, in many ways, to the igneous rocks which make up the Martian surface, allowing the production of a preliminary guide to Martian fossils.
“We propose a ‘volcanic microfossil atlas’ to help select target sites for missions seeking evidence of extraterrestrial life, such as the NASA Mars mission 2020 and ExoMars. The atlas could also help us recognize what Mars microfossils might look like, by identifying biosignatures associated with different types of fossilized microbes,” states Dr. Magnus Ivarsson of the Swedish Museum of Natural History.
“Studying whether there’s life on Mars or studying how the universe began, there’s something magical about pushing back the frontiers of knowledge. That’s something that is almost part of being human.”
Sally Ride — First American woman in space
The structure of ancient fossils can provide a vast amount of information about life from billions of years in our past. By studying carbon isotopes, as well as chemical information within the rocks, researchers are able to produce detailed analysis of these archaic structures. This study could help determine which kinds of life may have been preserved in igneous rock, as well as the conditions under which they may have formed.
The Past and Future of the Red Planet
Mars was once a water planet, but lost most of its atmosphere and water billions of years ago, possibly due to powerful dust storms that traverse the planet. Despite having a desert-like climate, Mars remains one of the best places in the Solar System to find extraterrestrial life.
The ExoMars mission consists of a rover, built by the European Space Agency (ESA), and a stationary science laboratory, designed by scientists and engineers from Russia. The rover is named in honor of Rosalind Franklin, a pioneer in genetics research who deduced the structure of DNA before Watson and Crick.
The Mars 2020 mission will examine the Martian crust, and seal samples of the Martian crust in containers, ready for a journey to Earth by a future mission. By looking at fossils from the earliest age of life on Earth, we may soon have a better idea of which rocks to examine, and maybe (one day) bring to laboratories here on our own planet.