On August 9, NASA’s Curiosity rover picked up samples from one of the most intriguing locations on Mars: the Vera Rubin Ridge.

What’s so special about the Ridge exactly?

The rover has never encountered a place with so much variation in color and texture, according to Ashwin Vasavada, Curiosity's project scientist at NASA's Jet Propulsion Laboratory, which leads the Mars Science Laboratory mission.

"The ridge isn't this monolithic thing — it has two distinct sections, each of which has a variety of colors," Vasavada said. "Some are visible to the eye and even more show up when we look in near-infrared, just beyond what our eyes can see. Some seem related to how hard the rocks are.”

Vasavada spoke with Tech Briefs about the importance of Curiosity’s latest find, and how NASA engineers are changing up their drilling methods to better understand Mars’ most captivating mountains.

Tech Briefs: Why is sampling the planet so important?

Dr. Ashwin Vasavada, Curiosity Project Scientist: It’s fair to say that Curiosity was built around its sampling capability. It’s big enough to transport two geochemical laboratories to Mars and to carry a large robotic arm with a jackhammer drill to acquire samples. After the Mars Exploration Rovers discovered evidence for sustained liquid water on ancient Mars, the next goal of NASA’s Mars Exploration Program was to understand the planet’s habitability — its capability to support life.

Only with laboratory techniques like mass spectrometry, gas chromatography, and x-ray diffractometry is it is possible to understand chemicals, nutrients, and organic building blocks necessary for life, and the minerals in the rocks that retain information about ancient environmental conditions. Within the first year after landing, results were used to describe a persistent, ancient freshwater lake within Gale crater that had the key chemical ingredients required by life, as well as organic molecules (those containing carbon, hydrogen, and other elements) that could be used by life.

Tech Briefs: Have any findings about the makeup of the planet surprised you?

Dr. Vasavada: On the one hand, it’s not surprising, since this is what Curiosity set out to find. On the other hand, there was always a risk that Mars wasn’t ever habitable. I’m surprised by just how habitable Curiosity has shown Mars to be.

Tech Briefs: What was the latest sample from Curiosity, and what did it reveal to us about Mars?

Dr. Vasavada: Curiosity is currently exploring the Vera Rubin Ridge, a wall-like topographic feature a few stories high and several miles long. Orbit-based spectrometers detected oxidized iron minerals on the ridge, suggesting that it may be unique from other rocks along Curiosity’s traverse in its composition and history. We’re particularly interested in understanding how those iron minerals got there, if they are related to why the ridge exists, and what the implications are for the history of water and habitability in Gale crater. The latest drill sample was our first from the ridge. It takes us a few months to fully analyze the data from the laboratory analyses, but we’re hoping to find answers to these key questions.

This 360-degree panorama was taken on Aug. 9 by NASA's Curiosity rover at its location on Vera Rubin Ridge. (Image Credit: NASA/JPL-Caltech/MSSS)

Tech Briefs: How does Curiosity drill for samples, and how has that method changed over the years?

Dr. Vasavada: In late 2016, the failure of a drilling attempt on Mars revealed that the drill feed motor had become unreliable. This motor moves the drill back and forth with respect to the rover’s arm. It was used in two ways: to push the drill bit while drilling with the arm fixed against the ground, and to retract the drill so that sample material could be transferred from the drill into the rover’s sample processing tools.

Project engineers spent several months trying to recover the motor, but in mid-2017, the focus turned to figuring out if drilling was possible without the motor. Through a mix of clever engineering, hard work, and good fortune, it turned out there were alternative ways of both drilling and transferring the sample material. Now we use the rover’s entire arm to control the drilling, much like holding a drill in your hand at home. We bypass the sampling tools altogether, and instead drop sample material directly from the drill bit into the rover’s laboratories. None of this was designed to work this way. I can’t overstate how incredible it was to see our engineers re-invent drilling on Mars and resurrect an incredibly important scientific capability from a hundred million miles away!

Tech Briefs: What will the next task for Curiosity be?

Dr. Vasavada: Our plan is to continue ascending Mount Sharp, a 3-mile-high mountain inside Gale crater. We’ve climbed over 1000 vertical feet already, and the evidence for lake environments has yet to cease. This means that habitable conditions persisted for a long time, at least tens of millions of years. We know from orbital data that higher layers on the mountain again change in composition, like at the ridge. So, our job is to understand what accounts for these differences and what the implications are for the habitability of ancient Mars.

Tech Briefs: How is Curiosity holding up, so to speak?

Dr. Vasavada: For a six-year-old rover that has driven over 12 miles, and explored hundreds of rock outcrops, Curiosity is doing great. With the drilling capability restored, the rover is nearly as scientifically capable as the day it landed. We’re slowing down gradually as our radioisotope power source degrades, but increases in efficiency and productivity have so far made up the difference. Nearly every day, hundreds of scientists around the world, including many students, are using the rover to make key discoveries using this priceless virtual presence on Mars.

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