NASA’s Perseverance rover on Mars has at last found a rock that’s a hard place.
After an initial failed attempt last month, the robotic prospector has successfully drilled two core samples from a Martian rock and stowed them away for eventual return to Earth.
An unexpected failure occurred in early August when Perseverance attempted to drill into a rock on the floor of Jezero Crater. This ancient lakebed is hoped to contain traces of past life.
That core disintegrated into dust, raising fears that the drill may have malfunctioned and ruined the sample.
But while the rock selected for the first sample was appealing because it appeared to be among the oldest rocks on the crater floor, it was also heavily weathered. That meant it might simply have been too soft, Jessica Samuels, the rover’s surface mission manager, said Saturday at a press briefing.
The team then turned its attention to a low ridge 560 metres to the west, because it appeared to be capped by a layer of tougher rock. A suitable contender (about the size of a mailbox) was identified, and Perseverance successfully drilled two samples out of it. Each core is about 6 centimetres long and the diameter of a piece of blackboard chalk.
The rover will carry these samples until enough are collected to create a cache. A future rover will then locate and retrieve the cache before delivering it to a lander. That, in turn, will launch the samples into space where an orbiting satellite will catch them before redirecting them to Earth.
It’s a multi-stage process that can’t possibly begin before 2026. That means the samples won’t arrive on Earth before 2031 at the earliest. But, with the first two samples literally in the can, NASA’s Planetary Science Division Director Lori Glaze says “[this] can be officially declared as the start of the Mars sample-return relay”.
“While it was a long time waiting, it feels fantastic,” she adds.
Matt Robinson, Perseverance’s strategic sampling operations team chief, adds that it’s proof of the capabilities of super-complex robotic systems. With its robotic arm, coring drill and intricate methods for containing, sealing and storing the sample, he says “[this] is the most complex mechanism ever flown into space”.
Read more: Insight into the Martian underworld
Meanwhile, scientists are already learning from the samples.
Before drilling into a rock, the rover uses an abrasion tool to rub away the top few millimetres of weathered surface to see what’s inside, “just like geologists in the field who hammer a rock to see a fresh surface,” says Julia Goreva, the team’s return sample investigation scientist.
But instead of looking at the exposed surface with the naked eye or a magnifying glass, the rover activates various precision instruments. These look for clues as to what the rock is made of—and whether or not it is worth drilling.
What Perseverance found was that the rock was probably volcanic. This is useful because volcanic rocks are easy to date via the decay of long-lived radioactive elements such as uranium. This, in turn, helps scientists puzzle out the chronology of events in Jezero Crater – including the emergence and disappearance of the potentially life-supporting lake they know once filled it.
But the instruments also spotted grains of what appears to be mineral salts deposited long ago by percolating water. This is important, Goreva says, because salt grains like these might retain microscopic bubbles of billion-year-old water. If so, these would allow scientists back on Earth to peer back to the dawn of Martian history.
Meanwhile, the rover’s mission is to rove. It’s already headed for its next sample site, a mere 200 metres away, called South Séítah. It’s a zone of low ridges, sand dunes, boulders and rock shards. NASA Jet Propulsion Laboratory mission scientist Ken Farley compares this terrain to “broken dinner plates”, offering another chance to reconstruct the sequence of events that shaped the crater and its one-time lake.
After that, the geological treasure hunt continues.
“Our job’s not done,” Robinson says. “We have an additional 35 sample tubes [for] samples.”
Richard A Lovett
Richard A Lovett is a Portland, Oregon-based science writer and science fiction author. He is a frequent contributor to Cosmos.
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