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Nasa’s Mars Perseverance rover has collected samples of Martian rock that appear to have been previously altered by flowing water.
Perseverance first landed on Mars in February 2021 after a gruelling seven-month, 293-million-mile journey from Earth. Its multi-year mission is to scour the planet’s surface for signs of ancient microbial life with the ultimate goal of returning samples back to Earth and potentially pave the way for future human visitors.
The latest rock samples come from the floor of the Jezero crater, where Perseverance currently resides, which was chosen as the study site because it sports a large river delta that once flowed into an ancient lake. Scientists believe that a watery Mars could have supported life billions of years ago.
“These kinds of environments on Earth are places where life thrives. The goal of exploring the Jezero delta and crater is to look in these once-habitable environments for rocks that might contain evidence of ancient life,” said Amy Williams, a professor of geology at the University of Florida.
Williams is one of the long-term planners for the Perseverance mission and helps decide where to send the rover and what tests and samples to prioritise.
Since its landing, scientists have explored the geological makeup of the Jezero crater floor using a suite of tools on board the rover that can take pictures of and analyse the chemical composition of rocks, as well as see their structure in the subsurface.
The scientific team discovered that the crater floor had eroded more than they expected. The erosion exposed a crater made up of rocks formed from lava and magma, known as igneous rocks. The rock composition is similar to some Martian meteorites.
The scientists originally expected that sedimentary lake or delta rocks would lay on top of these igneous rocks. It’s likely that the softer sedimentary rocks wore away over eons, leaving the tougher igneous rocks behind. The rocks the scientists analysed and stored for return to earth have been altered by water, further evidence of a watery past on Mars.
“We have organisms on Earth that live in very similar kinds of rocks,” Williams said, “and the aqueous alteration of the minerals has the potential to record biosignatures.”
Nasa and the European Space Agency are planning to return the rock samples to Earth around 2033. The ambitious plan requires building the first vehicle that can launch from the surface of Mars and rendezvous with an orbiter that ferries the samples back to Earth.
The payoff for that Herculean task will be highly detailed studies of the rock samples that cannot be performed on the rover. These studies include measuring the age of the rocks and looking for signs of ancient life.
As the rock samples taken at the bottom of the crater likely predate the river delta, dating these rocks will provide important information about the age of the lake.
In April, Perseverance recorded what is believed to be the first-ever Martian sounds which fall within the human audible spectrum, between 20Hz and 20kHz.
Mars is thought to be very quiet, with the team mistakenly believing that the microphone was no longer working on several occasions as it failed to pick up any noise. Apart from the wind, natural sound sources are rare.
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