Mars was wet once, according to a Martian meteorite found on Antarctica. This particular Mars rock turns out to be very special.
It was born in a lava flow 1.3 billion years ago and was ejected from the Martian gravitational field by an ancient impact with an asteroid or a comet. The impact ejected millions of tons of Mars rocks into space, aided and abetted by the relatively weak Martian gravity. Approximately 120 Martian rocks have been found on Earth so far from a succession of these collisions, and more are expected to show up as time goes on.
This particular Mars rock spent 12 million years wandering around the Solar System before it dropped in on Antarctica. Then it spent 50,000 years waiting for someone to come around to pick it up, which is exactly what the Japanese Antarctic Research Expedition did in 2000 when they found the rock on the Yamato glacier ice sheet.
There have been other very interesting Mars rocks found over the years, but this one is special because it shows definite signs of water erosion consisting of tunnels and micro-tunnels that were cut throughout the fabric of the rock by running water before it ever got here. There was a special bonus in this Mars rock, a surprise: evidence of carbon rich deposits in the fabric of the rock, possibly indicating that some form of carbon based life once existed on Mars.
Mars rocks found in other parts of the world might have been contaminated by coming into contact with liquid water after coming to Earth. The Antarctic Mars rock is different, because it landed on Antarctica and, having landed on Antarctica, it was never exposed to liquid water because there is no running water on Antarctica. Only ice. It is really beginning to look like Mars was wet once.
Scientists know that the rock had to come from space because there are no rocks lying around on the surface of the ice on Antarctica. They know this particular rock came from Mars rather than somewhere else because the rock’s chemical makeup is similar to the rocks that have been analyzed by the robots NASA scientists have sent to Mars. The guilty fingerprint appears to be the noble gas Argon, so named because it is inert and does not react with anything else. Mars appears to have a lot of argon in its atmosphere compared to Earth. The atmosphere on Mars is 1.6 percent Argon. The air on Earth is 0.93 percent Argon. Mars is the only place in the Solar System with an atmosphere that is 1.6 percent Argon. The rock came from Mars.
In 2011, another Mars rock was found lying around somewhere in the Sahara desert. Someone picked up, decided that it looked interesting and, eventually, it also ended up at NASA. In 2013, NASA announced that this Mars rock had ten times the water content of other Mars rocks that had already been found on Earth.
Not to be done, the 10 year-old Mars rover Opportunity found evidence just last month of the previous existence of water on the Red Planet. More specifically, the Rover found some very ancient clay deposits that were streaked with mineral deposits indicating that neutral pH water – the kind that humans can drink – once flowed through mineral deposits and deposited some of those minerals in a clay bank.
Now that scientists know that Mars was wet once, the next big question is where did the water go?
No one knows yet. It might be deep underground. It might locked into mineral deposits as water bearing rock. It might have been blown out to space by a tremendous meteor or comet strike. Or, maybe, it simply evaporated off the planet along with most of the planet’s atmosphere, which is now only one percent as dense as Earth’s is.
The only thing that is certain is that Mars was wet once according to those Martian rocks. And the Rover Opportunity agrees.
By Alan M. Milner