Debris from ancient volcanic eruptions on Mars could offer new clues in the search for alien life, a new study suggests.
The newly discovered rock type was found littered across the landing site of a future Mars rover mission due to launch in 2028.
In a study published last month in the Journal of Geophysical Research: Planets, researchers studied the rocks using data from orbiting satellites and concluded that they were likely laid down from the air, potentially as volcanic ash, billions of years ago. However, no volcanoes have been discovered at the site to date.
"There are no known volcanoes at this site, which means the debris probably came from hundreds or maybe even thousands of kilometres away," study first author Emma Harris, a doctoral student researching the geological history of Mars at the Natural History Museum in London, said in a statement. "It likely came from a really explosive volcano which launched ash high into the atmosphere and travelled this huge distance before settling at this site."
A dark mystery
Scientists think that the dark rocks may have protected mineral-rich rocks beneath, and it is these mineral-rich rocks that have the potential to preserve signs of life. However, little is known about how the surface rocks actually formed, the researchers say.
To learn more about these rocks, the study authors mapped a region of 19,300 square miles (50,000 square kilometers) using data from the Context Camera on the Mars Reconnaissance Orbiter, a NASA satellite that has been searching for evidence of ancient water on Mars since 2006.
The dark rocks are theorized to have once covered the whole site, but are now only found in smaller patches. The researchers propose that this is because the ash was preserved in areas of lower elevation inside impact craters, where it mixed with groundwater.
"The likely explanation for the location of these rocks is that upwelling of groundwater from within the crust once filled the bottom of these impact craters," Harris said. "When the ash fell on these patches of water, it made it stickier and more cemented. The rest of the ash which landed on the surrounding rock may have just blown away and never preserved."
The team hopes to learn a lot more about the site, known as Oxia Planum, once the ExoMars Rosalind Franklin rover mission arrives in 2028. The rover can't drive on the dark rocks because they're too jagged, but the study's findings suggest it could access mineral-rich rocks at the edges of the deposits.
Future missions to the Red Planet
The Rosalind Franklin rover mission has been heavily delayed, in part because of the war in Ukraine. The European Space Agency (ESA) cut ties with former partner Roscosmos, the Russian space agency, after Russia invaded Ukraine in 2022. That split caused the mission to miss its launch window in 2023.
In May 2024, NASA joined forces with ESA to complete the mission, Live Science's sister site Space.com reported. NASA was an original mission partner when the rover project started more than 20 years ago but dropped out due to budget issues.
The rover will be capable of drilling down into the surface of Mars and collecting rocks at a depth of 6.6 feet (2 meters), which it will then analyze in an onboard laboratory, according to ESA.
Researchers are targeting ancient rocks for their analysis because they think they are our best hopes for finding signs of life. The authors of the new study suggest that the dark rocks studied here were laid down around the middle Noachian and early Hesperian periods (4 billion to 3.7 billion years ago).
"These rocks are extremely old, but this is the time in Mars' history we want to be looking at," Harris said. "If life ever existed on Mars, it would have been a very long time ago because the planet has been arid and fairly inactive for the past three billion years. So we want to look at rocks before this period to see if there are traces of water or microbial life."
