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A Laboratory
on Mars

The most advanced scientific instruments to be used on Mars' surface will land in a crater near the planet's equator on August 5 at 10:31 p.m. Pacific Time.

The instruments are part of the Mars Science Laboratory (MSL), an ambitious NASA mission to set the Curiosity rover on a carefully selected site called Gale Crater. The mission's primary goal is to assess whether Mars is, or ever was, capable of supporting microbial life.

Michigan Engineering faculty, staff and students play roles in the mission's past, present and future.

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Chapter 1: Landing

An unprecedented landing technique will be used because Curiosity is larger than a Mini Cooper. It is twice as long and five times as heavy as twin rovers Spirit and Opportunity, launched in 2003.

To land, MSL will descend on a parachute and then use downward-firing thruster rockets to continue to slow itself. Then, during the final seconds before landing when the descent stage of the craft is 60 feet above the surface it will lower Curiosity to the ground using a tether, similar to a sky crane.

Landing

"Whenever I show someone NASA's video of the landing process, they're like, 'That's really cool, but also kind of insane,'" said Mark Pokora, a 2009 aerospace engineering grad who worked on an MSL-related project as a senior.

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The sky crane technique is being used to keep the craft's supersonic rocket jets as far from the surface as possible, minimizing their effects on the landing site. But the jets could still erode small craters into the Martian ground and kick up dust and particles in the process.

It is thanks, in large part, to a group of Michigan Engineering undergrads that NASA scientists understand this. Through class projects in a capstone design course in 2009, students performed the first tests to determine how much ground erosion the Mars Science Laboratory's landing process could cause, and how that could affect the rover.

Their class was taught by Nilton Renno, a professor of atmospheric, oceanic and space sciences, who is a coinvestigator on MSL's Rover Environmental Monitoring System. He and then-graduate student Manish Mehta had simulated the Mars Phoenix landing to see how pulsating exhaust plumes from the landing engines could affect the Phoenix. NASA engineers asked them to develop a similar test for MSL.

Over two semesters, student teams built a quarter-scale model of an MSL descent stage engine and designed an experiment to simulate the unique sky crane maneuver NASA developed to softly set its heaviest Mars rover down.

Pokora went to NASA Ames Research Center in Mountain View, Calif. with Mehta, the Ph.D. student, to do the experiments in a vacuum chamber that simulates the low atmospheric pressure of Mars, only 1/100 of Earth's. Ground walnut shells stood in for Martian soil in the planet's lower gravity acceleration. After dragging and emptying 50 bags of them into their Mars "sandbox," the team fired up their model and filmed what happened with a high-speed camera. They did 23 tests over three weeks exploring the effects of altitude, soil type, and thruster throttle level.

"It's a little surreal," Pokora said. "We did this testing as undergrads and now MSL is landing on Mars."

The analysis took months. Leslie Hall, another Michigan student and two-time JPL summer intern, processed the images to calculate the amount and velocity of the sand that was lifted.

"I'd go frame by frame and track certain particles to see how fast they were moving," Hall said. "There wasn't an 'Aha!' moment as much as an 'Uh-oh' moment when we realized that there was going to be more dust than originally thought."

Mars lander image

The MSL's thrusters are slightly canted in an effort to minimize ground erosion. In the students' test, they found that the small craters the tilted jets excavated could deflect the plume of dust and particles towards the rover, rather than away from it, said Renno and Mehta, who details the process in his Ph.D. thesis.

The team also discovered that the amount of erosion depends on the slope of the ground at the landing site and how compacted the soil is.

The rover's special thermal paint might be nicked, but it won't be stripped, the results showed. And the ground erosion would fortunately be outside the wheel-base on the rover. The findings did raise some eyebrows about a few instrument components that could be vulnerable to sandblasting, despite that nearly everything is shielded, Mehta said.

"When you do these subscale experiments, it's not a 1-to-1 match. It's a worst case scenario, but the fundamental physics of what is going on can be explored with a wide range of parameters. So the results were both groundbreaking and very useful to our engineering assessment," said Anita Sengupta, the senior systems engineer at NASA's Jet Propulsion Laboratory who initiated these tests and worked with the Michigan team.

Chapter 2: Exploring

Once on solid ground, Curiosity will begin to assess the habitability potential of the Gale Crater landing site. It will search for the building blocks of microbial life. One of MSL's scientific objectives is to search for organics, an umbrella term for molecules featuring carbon, the same molecules life on Earth is based on.

To search for organics, Curiosity will scoop up soil and drill inside rocks. As one of its many scientific objectives, the Sample Analysis at Mars (SAM) suite of MSL instruments, parts of which were built and tested at Michigan Engineering, will analyze the solid samples and the air the rover sniffs to determine whether organics are present. SAM has ovens to heat solid samples to temperatures as high as 2,000 degrees Fahrenheit, a process that is expected to release trace amounts of any organics present. This advanced equipment, mission scientists believe, is capable of detecting organics if they are present in the Gale Crater.

"Organics, whether or not connected to life, have never been positively identified on the surface of Mars, which seems puzzling considering that they have been raining down on Mars for 4.5 billion years, even if Mars never had its own source," says Sushil Atreya, a professor in the Department of Atmospheric, Oceanic and Space Sciences.

A science lead on the Goddard Space Flight Center's SAM instrument suite, Atreya contributed to the conceptual development of the MSL mission decades ago, and now he will lend his expertise on trace gases to the mission.

"I will be looking at the SAM measurements of atmospheric trace gases, and the gases evolved from solid samples along with their isotopic composition," Atreya says. "Methane is one such trace constituent, as its presence could signify either biological activity or complex water-rock reactions. By combining the SAM data on trace gases and the noble gases with mineralogical, geologic and environmental data collected by other instruments on MSL, I'll be examining the question of habitability and the climate evolution of Mars."

Comparing them with their values on Earth, Venus and meteorites will provide important insight into the climate and geologic history of the terrestrial planets.

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Even with advanced technology, organics are hard to find. Groundwater could have destroyed organics through oxidation on Mars, as is the case for many rocks on Earth that are billions of years old. Other chemicals detected on Mars can cause this oxidation as well, and there is also the destructive effect of radiation. The hope is that some organics will have survived after undergoing rapid mineralization.

If Curiosity does not detect organics, Atreya will remain optimistic.

"Their absence in the Gale Crater landing site would not necessarily imply that organics are absent from other parts of Mars. Even in the Gale Crater region, they could have existed at one time, even if they are not detected now."

Nilton Renno discusses the Mars rover

Atreya is looking forward to Curiosity's landing and the search for organics and trace constituents, he says, but he isn't a rookie when it comes to space discovery. He has been involved in over 10 planetary spacecraft missions, starting in 1974 with the Voyager missions to the giant planets.

"Nothing will ever beat Voyager. Every day, every moment had a discovery," Atreya says. In fact, the Voyagers continue to make discoveries as both Voyager 1 and 2 spacecraft are still sending scientific information about their surroundings outside the solar system through the Deep Space Network.

Still, Atreya states MSL is his most exciting Mars mission to date.

Ultimately, Curiosity's findings will be combined with findings from previous and current missions. This information, Atreya hopes, will be applied to extrasolar planets, which are planets outside the solar system. Armed with knowledge of the planets around our Sun, such as Mars, scientists can begin to study the possibility of life on extrasolar planets.

"We want to find out how life began here or elsewhere," Atreya says. "These are very profound, deep questions and with these kind of experiments, we're beginning to inch our way to addressing them."

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