Rocks from the early history of Mars – almost four billion years ago – suggest there might have been a habitable environment underneath the surface of the planet, according to an October 2010 report by NASA and the Planetary Science Institute. NASA planetary scientist Paul Niles is co-author of the report. He told EarthSky:
These rocks are evidence that there has been a sub-surface hydrothermal system on Mars that could provide a strongly habitable environment on Mars.
In other words, these rocks – exposed by an ancient meteor impact – show evidence of heat and water beneath the planet’s surface. Heat and water, says Niles, are necessary for an environment to be considered habitable.
You need to have liquid water, you need to have organic material, and you need to have heat. We don’t have evidence for organic material in these rocks directly, but we have two out of three. Finding evidence for organic material requires visiting that place with a surface mission.
According to Niles the rocks discovered in this study are rich in carbon – an essential ingredient for the formation of organic material, and life.
It’s hard to place odds on it without knowing more about how life evolved. And I think that’s why we need to go and learn more about these kinds of rocks.
The presence of these rocks was first detected with the Mars Reconnaissance Orbiter (MRO), a NASA satellite that orbits and captures images of the planet. Dr. Niles says the presence of water on the ancient Martian surface is a long-accepted possibility. He said:
When we first sent spacecraft to Mars to take pictures of its surface, besides showing volcanoes and big valleys, we saw evidence for water on the surface. We saw channels that looked like they had been carved by water. This was interesting because the current Martian atmosphere is very thin and does not support liquid water for very long periods of time.
The thinking has always been that Mars early in its history hosted liquid water, maybe oceans, or lakes, and had rainfall. But the puzzle is trying to figure out how did you get to a point where Mars could have had lots of liquid water on the surface? The thinking has always been that Mars had a denser early atmosphere with carbon dioxide as its main gas. Carbon dioxide reacts with water and forms carbonate rocks. And so the expectation was that we’d see a lot of carbonate rocks on the surface as well, and that has not been the case – in fact we’ve actually seen very few.
He said that the reason so few carbonate rocks have been found on the surface of Mars is because volcanic lava flows have covered much of the planet. Dr. Niles explained more about the geological conditions of our planetary neighbor.
Mars doesn’t have plate tectonics and the Mars surface is much older than what we see on Earth where most of the surfaces have been reworked or subducted. So Mars provides an opportunity to look back into the early history of the solar system and to understand how life may have evolved. I think the habitability and the evolution of life is one of the central questions driving Martian research.