A collection of rocks scattered along an ancient coastline on Mars indicates that, billions of years ago, the Red Planet became much more Earth-like than previously assumed. That is the main conclusion of a study led by researchers at the Los Alamos National Laboratory, in New Mexico, in which scientists from different international universities have participated. The work has just been published in ‘JGR Planets’.
The rocks, found and analyzed by NASA’s Curiosity rover, have turned out to be unusually rich in manganese oxide, a chemical that adds to growing evidence that early in its history, Mars once had levels of oxygen similar to those of our planet, and also ideal conditions for life.
The path to life
Here on Earth, manganese, whose presence paved the way for the oxygen on which most life today depends, was abundant in early rocks and oceans before the first living things arose around 4 billion years ago. years. And it played an important role in the evolutionary process that ended up turning our world into an inhabited place.
The only known ways to produce manganese oxide, however, involve the existence of one of two things: abundant oxygen or microbial life. And on Mars there is no evidence of one or the other, leaving scientists baffled and unsure of how this substance came to form in the newly discovered rocks.
Creating rocks rich in manganese oxide “is something easy to do on Earth,” explains Patrick Gasda, lead author of the study, “due to both the presence of microbes and oxygen (which also comes from microbes), so everything points towards life. “But we have no evidence of life on Mars, so nothing we know about the planet explains how oxygen could form in a fully abiotic system.”
promising rocks
While traveling through the center of Gale Crater, the ancient lake bed 154 km in diameter, the Curiosity rover came across a series of heavily eroded rocks, and one of its instruments, the Chem Cam, ‘sniffed’ manganese oxide present in rocks by vaporizing small fragments with a laser and analyzing the resulting plasma cloud. According to the study, the compound accounts for almost half of the chemical composition of the samples analyzed.
Furthermore, in the same place where it found the rocks, the rover recorded an elevation of between 10 and 15 meters. And although that is not much compared to the slopes of hundreds of meters that Curiosity has had to overcome over the years (it has been touring the crater since 2012) “it tells us that something special is happening in this place,” he says. Gasda. In fact, the texture of the rocks appears to have changed from ‘curved’ to ‘flat’, a change that researchers interpret as the channel left by a river making its way to a lake.
According to the researcher, “that means we are on the shore of the lake or near the shore of the lake.” An interpretation, however, that is uncertain due to the scarcity of data, since Curiosity passed through that place only once. Still, says the scientist, “this is our best hypothesis.”
If the idea is correct, the rocks may have been deposited in their current location when the river water slowed down as it entered the lake, just as rocks rich in manganese oxide have been found on the shores of shallow lakes. deep in the Earth.
One more proof, therefore, of the existence of liquid water in the Martian past, and of the presence of a much higher amount of oxygen than previously thought, comparable to what exists on our own planet.
