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NASA’s Curiosity rover finds more evidence that Mars was once habitable

The robot is learning a lot from its mountain trek

Comparisons of Curiosity’s location on Mount Sharp — today and billions of years ago.

As NASA’s Curiosity rover makes its way up a layered mountain on Mars, the little bot is finding even more signs that the Red Planet was once a habitable place — potentially capable of hosting microbial life billions of years ago. The rover has been drilling as it climbs, and the samples it has uncovered reveal this region of the mountain to have a variety of minerals, chemistry, and textures. These diverse samples are helping scientists paint a picture of how ancient groundwater interacted with these rocks and changed over time.

Since water is such a key ingredient for life here on Earth, its past presence on Mars may mean that life once thrived there, too. “We’re finding different habitable environments as we go along,” Joy Crisp, a deputy project scientist for the Mars Science Laboratory at NASA, tells The Verge.

Curiosity landed on Mars four years ago in an area called Gale Crater, where it has discovered things like organic matter and an ancient streambed that have raised the possibility of Mars’ past habitability. Since then, the rover has traveled over nine miles and is currently climbing up a mountain in Gale Crater called Mount Sharp. The farther up Curiosity gets, the more diverse types of rocks it finds.

The path of NASA’s Curiosity rover so far.

Specifically, Curiosity has found boron for the first time on this trip. It’s an element that’s never been found on Mars before, and its presence on the planet is exciting because it’s very water soluble. Typically, boron is found in places where water has evaporated, leaving the element behind. Even more tantalizing is that Curiosity has found this boron inside mineral “veins” on Mount Sharp. These veins are cracks in the Martian rocks that are filled with chemicals. It’s thought that these chemicals used to circulate inside ancient groundwater on Mars. When the groundwater eventually evaporated, the chemicals were leftover in the cracks.

As for the source of this groundwater, one idea that NASA has is that there used to be a lake at Gale Crater, and boron was trapped in the rocks underneath it. Eventually that lake disappeared on the Martian surface, but it didn’t totally go away. Instead it retreated underneath the rocks as groundwater. And that groundwater had the right chemistry that allowed it to extract the boron from the rocks and deposit it in these mineral veins.

If that’s true, that means this groundwater may have been particularly habitable at some point. Not only was it a liquid, but it was probably warm and not too acidic in order to dissolve the boron. So even regular bacteria could have permeated these waters. “It’s telling us this water is very interesting and has this dynamic chemistry,” Patrick Gasda, a post-doctoral student at Los Alamos National Laboratory, tells The Verge. Researchers also think that the groundwater reacted with the bedrock over time, changing the chemistry of both the water and the rock. And it’s these types of chemical reactions that support life here on Earth.

Of course, no direct signs of ancient life have been found just yet on Mars. But the evidence of this groundwater system potentially extends the period of time when Mars could have been habitable. And that increases the odds that life formed there.

As exciting as Curiosity’s findings have been, the rover’s trip up Mount Sharp may be stalled for a bit. Last week, NASA said it was having trouble extending Curiosity’s drill, so NASA put Curiosity’s trip on pause while engineers at the space agency try to figure out what’s wrong. In the meantime, Curiosity is “studying its surroundings and monitoring the environment” on Mount Sharp, but it won’t be going anywhere for now.

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