Earth rock testing to help NASA’s rover work on Mars

Shrimp-like rock test: Engineers working with NASA’s Mars rover created this test area at JPL to practice drilling in crumbly rock using a duplicate of the rover’s rock drill bit. The first sample of persistence crumbled to a powder instead of remaining intact, prompting a test campaign. Credit: NASA/JPL-Caltech

Using carefully selected ground rocks, engineers are trying to figure out how to handle crumbly rocks like the ones the probe encountered on its first sampling attempt.

Creating a Drill Hole in a Test Rock: Engineers at NASA’s Jet Propulsion Laboratory conducted tests on rocks like this one to understand why the agency’s Perseverance rover’s first attempt yielded a powder sample. A duplicate of the rover drill attempted to create a core out of crumbly rock. Credit: NASA/JPL-Caltech

when[{” attribute=””>NASA’s Perseverance Mars rover tried to collect its first rock core sample last August, the outcome presented a puzzle for the mission team: The rover’s sample tube came up empty. But why?

Not long after, Perseverance successfully gathered a sample the size of a piece of chalk from a different rock. The team concluded that the first rock they had chosen was so crumbly that the rover’s percussive drill likely pulverized it.

But engineers at NASA’s Jet Propulsion Laboratory in Southern California, which manages the mission, want to understand why that first sample, nicknamed “Roubion,” turned to dust. The mission’s scientists and engineers had run extensive test campaigns on dozens of rock types prior to launch, but they hadn’t seen any react exactly like Roubion.

So a new test campaign was started – one that would include a field trip, a duplicate of Perseverance’s drill, and JPL’s unique Extraterrestrial Materials Simulation Lab. Answers remain elusive, but here’s a closer look at the process.

How do spacecraft deal with dust storms on Mars? Get the latest news on the rest of NASA’s Mars fleet with our Mars Report. The new release focuses on the last dust storm on the red planet. Watch how the agency’s orbiters supported the InSight lander as its power decreased during the January event. Source: NASA / JPL-Caltech / ASU / MSSS

Remember Ropion

Recreating the unique physical properties of Roubion will be key to the test campaign.

“Of the rocks we saw, robin had the most evidence of interaction with water,” said Ken Farley of the California Institute of Technology, Perseverance Project Scientist. “That’s why he collapsed.”

Rocks that are altered by the action of water can be more prone to collapse; It is also of high value to perseverance scholars. Water is one of the keys to life – on land at least – which is why Perseverance explores Jezero Crater. Billions of years ago, Jezero Island had a lake fed by rivers, making it an ideal place to look for signs of now ancient microscopic life. Perseverance is collecting samples that future missions can bring back to Earth to be studied in labs with powerful equipment too big to be sent to Mars.

Aerial shot of Santa Margherita Ecological Reserve: A drone captured this view of members of NASA’s Persistent Mars Probe Team at the Santa Margarita Environmental Preserve in Southern California as they search for crumbling rocks for a test expedition. Credit: NASA/JPL-Caltech

field trip

To find Roubion’s backup positions, a few members of the probe team were given permission to fish for rocks at the Santa Margherita Ecological Preserve, a two-hour drive from the Jet Propulsion Laboratory. The team was looking for rocks that would fill a good geologic spot: they were weathered enough to be similar to propion, but not so brittle that they might disintegrate at the slightest touch. They eventually chose half a dozen rocks.

“It was very physical work,” said Louise Gandora of Jet Propulsion Laboratory, chief engineer for sampling and buffering, who led the test campaign. “We were cutting with rock hammers and levers. A couple of rocks were big enough that we all needed to stick a stretched-out rag to get them into the bed of our truck.”

Next step: testing at the Jet Propulsion Laboratory. One place where this happens is the Extraterrestrial Materials Simulation Laboratory, which is a kind of service center that prepares materials for testing elsewhere in the JPL.

Rock Hunters at JPL: Members of the Jet Propulsion Laboratory team that went searching for Mars-like rocks in the Santa Margherita Ecological Preserve pose for a selfie. From left: Erin Dallchog, Iona Brockie, Louise Gandora, Ken Farley, and Sarah Yericks. Credit: NASA/JPL-Caltech

Superstore Rock

The low-rise building is located on a hillside above Mars Yard. The outer drums contain a reddish dust called Mojave Mars Simulant, a special recipe for re-creating the chaotic conditions into which roving vehicles travel. Piles of rocks – some full of drilling holes – are scattered around a forbidden industrial saw near the entrance. In the back stands a concrete bunker with rock chests with names that sound like Mad Libs to geologists: Old Dutch Pumice, China Ranch Gypsum, Bishop Tuff.

“I like to say we do the artisanal selection and preparation of materials,” said Sarah Yerkes, a mechanical engineer who leads the lab. “Testing it is part manufacturing and part crazy science.”

Yerix is ​​one of the people who picked rocks on the Santa Margherita Ecological Preserve trip. To test on Roubion-like boulders, the Yearicks team worked with a structural-grade drill bit — not a bore drill — along with other tools, while the Jandura team used a “fly-like” version of their persistence drill. Samples back and forth, tested in different ways.

Close-up of a perseverance-like exercise: This drill is a replica of the drill aboard NASA’s Mars probe. It was used in a test campaign to see how the friable rock would respond to drilling. Credit: NASA/JPL-Caltech

Put to the test

Jandura’s team performed their flight-like pits a few millimeters at a time, stopping to check that the nucleus was still forming; If it collapses, they will look at the variables that might be the cause. For example, engineers adjusted the drill’s percussion rate and the weight that was placed on the drill bit. They also tried to drill into the rock horizontally rather than vertically, in case debris buildup was a factor.

For every adjustment they make, it seems, a new wrinkle will appear. One was that the brittle specimens still resisted the percussion drill. When Jandura’s team reduced the force of the percussion to avoid turning the sample into powder, the drill bit could not penetrate the surface. But choosing a place that tolerates a stronger knock means choosing a place that interacts less with water.

Perseverance has so far captured six samples of highly weathered and water-changed rock, and the team knows it’s capable of doing many more. But their experience with Roubion prepared them for some of the extreme cases that Mars will throw on perseverance in the future. If they find more rocks like Roubion, the Extraterrestrial Materials Simulation Laboratory will be ready with a batch of Mars-worthy materials.

More about the mission

Astrobiology is one of the main goals of the persistence mission to Mars, including the search for signs of ancient microbial life. The rover will characterize the planet’s geology and past climate, pave the way for human exploration of the Red Planet, and will be the first mission to collect Martian rocks and regolith (fractured rock and dust) and store them in a cache.

Subsequent NASA missions, in cooperation with the European Space Agency (ESA), will send spacecraft to Mars to collect these sealed samples from the surface and return them to Earth for deep analysis.

The Mars 2020 Perseverance mission is part of NASA’s Lunar-to-Mars Exploration Approach, which includes the Artemis missions to the Moon that will help prepare for human exploration of the Red Planet.

The Jet Propulsion Laboratory, operated by the NASA-administered California Institute of Technology in Pasadena, California, built and operated the rover’s operations.