Between 4.1 and 3.9 billion years ago today, Mars – just like the Earth – would have suffered what astronomers call a great meteorite bombardment. But researchers are questioning this theory today. According to them, the impacts stopped well before those on our planet, leaving room for conditions conducive to the appearance of life.
In its youth, Mars was violently hit by giant meteorites. Astronomers have suspected that for a long time. But a team from Western University (Canada) shows today that the bombing had ended earlier than planned. That makes it more likely that Mars could have had life, because as long as the meteorites fell on Mars, the planet had to be extremely inhospitable. Let’s remember that on Earth, scientists estimate that the first traces of a rudimentary life could have appeared more than 3.5 billion years after the bombing of meteorites faded around 3.8 billion years. And astronomers thought that the same timing was applicable to Mars.
However, researchers at Western University now estimate that on the Red Planet, the great bombing ended 4.48 billion years ago.
Did life appear on Mars before emerge on Earth?
To obtain their results, the researchers draw from analysis conducted on meteorites found in the Sahara Desert, rocks that they suspect come from the highlands of southern Mars. But these contain elements – grains of zircon and baddeleyite – that allow geologists to determine their age very reliably.
Scientists can read a kind of history of pressure shocks like those that happen when a rock is struck by a meteorite. But in their samples, researchers at Western University found few traces of high-impact events more recent than 4.5 billion years ago.
“The impacts of giant meteorites on Mars could, at first, have accelerated the release of the first waters from the inside of the planet. Then, they would have stopped. That would have opened the door to life-giving reactions,” says Desmond Moser, a researcher at Western University.