Impact glass, formed from the heat produced when a meteorite or comet smashes into the surface of a planet, has been found in craters on Mars, NASA announced Monday.
On Earth, impact glass has been shown to encase and preserve plant matter and organic molecules for millions of years.
"Knowing that impact glass can preserve ancient signs of life — and now knowing that such deposits exist on the Martian surface today — opens up a potential new strategy in the search for ancient Martian life," NASA said in a statement.
Kevin Cannon and Jack Mustard at Brown University in Providence, R.I., looked for signs of impact glass in data from the Mars Reconnaissance Orbiter's imaging spectrometer for Mars. The device scans Mars's surface, looking for the "fingerprints" of various minerals — different materials have different fingerprints because they absorb more light of some colours than others. Some of those colours are visible to humans and others are in the invisible range known as "infrared."
To figure out what the fingerprint of impact glass on Mars would look like, Cannon and Mustard took powders with a similar chemical composition to those on Mars and heated them up until they melted them into glass. They measured the fingerprint for that glass and looked for a similar fingerprint on Mars.
They found it right in the middle of some craters, on features called the central peaks — mounds that often form in the centre of a crater when a meteorite strikes.
The findings were published in the journal Geology.
Now that the impact glass has been found, it's something future Mars rovers could look for, suggested Jim Green, director of NASA's planetary science division, in a statement.
In fact, one area where impact glass was found is close to one of the potential landing sites for the Mars 2020 rover, scheduled to launch in 2020. It will collect soil and rock samples that may one day be sent back to Earth.
The Mars Reconnaissance Orbiter was launched by NASA in 2005 and has been orbiting Mars since 2005, looking for evidence that there was water on the surface of the Red Planet for a long period of time.