Bacterial fry-up: Living and fossil samples of bacteria were attached to the heat shield of the ESA's Foton M3 spacecraft.
Credit: ESA
Mars rocks
"However, the results are more problematic when applied to panspermia," she said. "STONE-6 showed at least two centimetres of rock is not sufficient to protect the organisms during [atmospheric] entry."
So far 39 meteorites have been found on Earth that have been attributed, through their chemical signature, to a Martian origin.
The notion is that they were knocked off the planet in the distant past by an asteroid impact. They then wandered in space before landing here. But all of these meteorites are of basalt, or volcanic origin.
Perplexing find
None is sedimentary, a term for rocks that are laid down in beds or strata as a result of wind, water or gravity. This has perplexed scientists, as there is abundant evidence for sediments on the Red Planet.
The outcome of the STONE-6 experiment, though, shows that Martian sedimentary rocks could survive entry through Earth's atmosphere.
The Foton M3 capsule generated temperatures of around 1,700 ºC, although its speed was somewhat slower than that of a meteorite. Meteorites normally attain a velocity of 42,800 to 53,600 km/h, depending on their angle of descent. A third piece of rock, a control sample of basalt, was lost during the descent.
Panspermia
This experiment is hardly the end of panspermia - how about using a rock the size of a car, with lots of cracks and fissures, where bacteria has been found living at great depths of Earth's mantle.
All the French have proven is that bacteria has a rough ride on a re-entering nose cone!
Panspermia
I agree with the previous comment. Assuming that the cooling Earth continued to be quite heavily bombarded for perhaps hundreds of millions of years by rocks of all sizes, the solitary experiment in question can hardly be of great significance.
Of course, were not even talking of the abundant complex prebiotic precursor molecules observed in relatively local regions of interstellar space, and it may be even more likely that those were our ancestors.