The famous “Conan, the bacteria” (Deinococcus radiodurans) could have survived an ejection on Mars and reached Earth
A new experiment with one of the most resistant bacteria on Earth reinforces the lithopanspermia hypothesis: the idea that life can travel between planets inside rocks dropped by asteroids.
Rocks from Mars have already reached Earth. Scientists found them: meteorites with a chemical signature that could only originate from the Red Planet, scattered across Antarctica and other remote corners of the globe.
The question that has never been answered so far is whether something alive could have survivedor on the trip.
A team from Johns Hopkins University has now decided to test the most brutal part of this scenario: the moment an asteroid falls on Mars and projects rock fragments from the surface to space.
Could a living organism resist to that initial, violent launch?
The team chose one of the most resistant bacteria known on Earth, subjected her to conditions designed to replicate ejection caused by a Martian impact and observed what happened.
The results, published on Tuesday in PNAS Nexusextend the limits of survival far beyond than previous impact experiences had shown.
At pressures comparable to those that launch rocks from Mars at escape velocity, the bacteria Deinococcus radiodurans survived with rates close to 95%. This places this work at the center of an old debate: the hypothesis of litopanspermiaaccording to which life can move between planets aboard rocks dropped by asteroids.
Previous research had already shown that this microorganism can withstand the radiation, cold and dehydration of interplanetary space. Now, everything indicates that it is also capable of surviving the launch phase, at least under some realistic ejection pressures, writes .
A Deinococcus radiodurans not a typical laboratory microbe. This bacteria was first identified in the 1950s inside a can of ground beef that had been sterilized with radiation — and yet there was something alive inside.
Since then, it has become the standard of biological robustness: resists radiation, drought, extreme cold and the vacuum of space. Passes virtually all tests that the researchers put to him.
A Deinococcus radiodurans It is so incredibly resistant that it earned the expressive name ““.
What had never been tested was his response to impact pressures at high speed, the kind generated when an asteroid hits a planet. This gap was crucial, as the launch phase of any interplanetary journey would expose possible microbial “passengers”It uses some of the most intense mechanical forces imaginable.
To recreate a planetary impact, the team of researchers adapted a “gas cannon” originally built to study the behavior of materials under extreme stress.
A metallic projectile was fired at a target assembly that contained a thin layer of bacteria sandwiched between two steel plates. Each collision only lasted microsecondswith pressures measured in real time by laser-based sensors.
In parallel, the team analyzed control samples — identical bacteria that had undergone all stages except impact — to accurately isolate the effect of collision on survival.
The shots were made at pressures between 1.4 and almost 3 gigapascals. One gigapascal is equivalent to about 10,000 times atmospheric pressure at sea level on Earth.
Computer models suggest that rocks ejected from Mars at escape velocity are generally subjected to pressures of less than 5 gigapascals, which puts the team’s experiments within the plausible range for real ejections.
Survival rates that change the search for life on Mars
A 1,4 gigapascais, a D. radiodurans survived in about 95% of casesin several tests. The survival dropped to around 86% at 1.9 gigapascals and for approximately 60% at 2.4 gigapascals.
Close to 3 gigapascals, survival continued to be detectable, but it fell sharply: the test at 2.9 gigapascals produced less than 10% of survivors, although the exact rate has been difficult to determine precisely due to experimental limitations.
All tests used actively growing cellsand not dormant spores — which tend to be more resistant.
“Our results suggest that microorganisms can survive conditions much more extreme than previously thought previously, being able to withstand conditions that result in the formation of ejecta capable of moving through planetary systems,” the study authors wrote.
Martian rocks have already reached Earth. The question now is not just whether travel is physically possible — but If anything, ever, came on board.
