The surface of Mars is pocked by more than 635,000 impact craters at least 0.6 miles (1 kilometer) wide. Each of the red dots shown on the image below represents one of the impact craters. A little-known fact is that each year Earth is hit by by half a dozen or so one-pound or larger rocks that were blasted off the surface of Mars by large impacts and found their way into Earth-crossing orbits. Nearly 10% of the Red Planet meteorites end up crashing into Earth.
This natural “interplanetary transportation system” begs a fascinating question: If primitive and nearly indestructible micro-organisms exist on a given planet, must they by definition as a natural act of nature, travel to their immediate solar-system neighbors?
The NASA image above shows the Rabe Crater, which lies among hundreds of thousands of other impact craters in the rough-hewn southern highlands of Mars. Spanning 108 kilometers (67 miles), Rabe is halfway between the martian equator and the south pole, and west of the giant impact basin Hellas. Two features distinguish Rabe Crater apart from most other craters on Mars. The crater has a flat floor with a pit sunk into it, plus a large field of dunes
Recent research on lunar rocks discovered in Antarctica has shown that rocks greater than 10 kilograms in mass could be ejected from terrestrial planets -these are rocks capable of carrying living microbes- and survive the searing violence of the launch. Over the history of the Earth, billions of football-sized rocks have landed on its surface, some only slightly heated by the launch, reaching Earth in a matter of a few months.
This week it was announced that a team of geologists has discovered that a meteorite housed in the Royal Ontario Museum started as a 200 million-year-old lava flow on Mars, and contains an ancient chemical signature indicating a hidden layer deep beneath the surface that is almost as old as the solar system.
By directing energy beams at tiny crystals found in a Martian meteorite the geologists has proved that the most common group of meteorites from Mars is almost 4 billion years younger than many scientists had believed – resolving a long-standing puzzle in Martian science and painting a much clearer picture of the Red Planet’s evolution that can now be compared to that of habitable Earth.
"Basically, the inner solar system is our oyster. We have hundreds of meteorites that we can apply this technique to, including asteroids from beyond Mars to samples from the Moon," says lead author Desmond Moser, an Earth Sciences professor from Western University’s Faculty of Science. Moser estimates that there are roughly 60 Mars rocks dislodged by meteorite impacts that are now on Earth and available for study, and that his group’s approach can be used on these and a much wider range of heavenly bodies.