A new study has found evidence that the energy released by meteorite impacts on Mars would wipe out any signs of life inside the craters they leave behind. And that's a problem, seeing as impact craters have long been considered the best place to look for life on the Red Planet.
That might sound pretty depressing, but the implications are actually pretty promising - we've been so focussed on impact craters, we might have a false impression of how lifeless Mars actually is.
"The study is helping us to see that when organic matter is observed on Mars, no matter where, it must be considered whether the sample could have been affected by the pressures associated with blast impacts," team member Wren Montgomery from Imperial College London said in a statement.
"We still need to do more work to understand what factors may play an important role in protecting organic compounds from these blast impacts."
Before we get into the new findings, it’s important to point out why impact craters have been such a target for researchers searching for signs of life.
According to Montgomery and his colleagues, the basic idea is that meteorite impacts can cause rocks from deep below the surface to get ejected onto the top of the surface, making them easier to study.
Since these rocks were impossible for researchers to get to - before they were blasted all over the surface from the impact - they should offer a unique glimpse into the planet’s past. The idea is that impact craters are a natural way for researchers to dig deeper than they can with a rover.
But that way of thinking could soon be turned on its head, because a meteorite impact potentially has enough power to completely obliterate the type of organic matter researchers are hunting for - long chain hydrocarbons.
To figure this out, the team replicated a series of impacts caused by meteorites measuring about 10 metres (32.8 feet) in diameter and examined how those impacts could theoretically affect the organic matter.
They pulled this off by placing various organic compounds inside a piston cylinder device, subjecting the compounds to the same amount of pressure that would result from a meteorite strike. They then used chemical analysis techniques to examine the changes.
In the end, they found that typical meteorite impacts produce enough energy to destroy long chain hydrocarbons and chemically alter aromatic hydrocarbons, concluding that impact craters might not be the best place to search for signs of life.
"We’ve literally only scratched the surface of Mars in our search for life, but so far the results have been inconclusive. Rocks excavated through meteorite impacts provide scientists with another unique opportunity to explore for signs of life, without having to resort to complicated drilling missions," said team member, Mark Sephton.
"Our study is showing us is that we may need to be nuanced in our approach to the rocks we choose to analyse," he added.
It’s important to note that the team only studied how organic matter changes under one amount of pressure - that of a 10-metre (32.8-foot) diameter meteorite - so they'll need to experiment with a variety of pressures before they can say for sure that most impact craters have the power to destroy organic material.
Until then, the team is urging scientists to be a little more selective with the rocks they choose to study. If they do, they might have a better chance at finding signs of life on Mars.
The team’s findings were published in Scientific Reports.