For Mars sample return, Perseverance is required
NASA’s newest Mars rover needed a name, so NASA turned to the experts: kids. Just as it did with previous Mars rover missions, including Spirit, Opportunity and Curiosity, the agency held a nationwide contest, inviting students to submit essays describing their proposed names for the rover flying on the Mars 2020 mission. Rounds of judging and online voting followed.
NASA unveiled the winning name in early March: Perseverance, proposed by Alexander Mather, a seventh grader in northern Virginia. “If you think about it, all of these names of past Mars rovers are qualities we possess as humans,” he wrote in his winning essay. “But, if rovers are to be the qualities of us as a race, we missed the most important thing. Perseverance.”
Scientists and other Mars exploration advocates know the importance of perseverance, given the delays and setbacks they’ve encountered over the years. That’s especially the case in the quest to return samples of Mars to Earth. Mars 2020 will, at last, start that effort.
A NEW MISSION, A NEW VEHICLE
The concept of Mars sample return has been around for decades. The idea is straightforward: bring Mars rocks to Earth, where scientists can study them in labs in far greater detail than possible with instruments sent to Mars on spacecraft.
“One of the really key questions that is almost impossible to answer with spaceborne instrumentation is the definitive documentation of life beyond Earth,” said Ken Farley, Mars 2020 project scientist. “That has such a huge burden of proof that we don’t expect to be able to do that with instruments that are flyable.”
While the concept is simple, the execution is not. Although sample return from the moon can be done with a single mission, as the Soviets did several times in the 1970s, a single Mars sample return mission would be far too large to launch on any rocket. A series of missions is needed to collect samples and send them to Earth.
In the late 1990s, NASA and the French space agency CNES studied concepts for a Mars sample return mission proposed for launch as early as 2005. NASA would fly one or more landers to collect samples and launch them into Mars orbit, while a CNES orbiter would grab the sample and return it to Earth. The failures of NASA’s Mars Climate Orbiter and Mars Polar Lander missions in 1999, though, scuttled those plans.
Mars sample return returned to the forefront in 2011. The planetary science decadal survey recommended as its top flagship mission the Mars Astrobiology Explorer Cacher, or MAX-C, a rover that would search for evidence of past life on Mars and also collect, or cache, samples that would be returned to Earth “eventually.”
In December 2012, buoyed by the success of Curiosity’s landing four months earlier and the public interest in that mission, NASA announced its intent to proceed with something like MAX-C. The agency said it would launch a rover similar in design to Curiosity in 2020 intended to “advance the science priorities” of the decadal survey.
That rover mission would become Mars 2020. “At first glance, it looks a little bit like Curiosity,” said Matt Wallace, the deputy project manager for Mars 2020. “We have been able to leverage a lot of the investment that was made for Curiosity.” That includes the design of the rover as well as its “skycrane” landing system made famous by Curiosity’s “seven minutes of terror” landing.
Perseverance, though, is not a copy of Curiosity. “This vehicle is a new mission, a new vehicle and with new capabilities,” he said. After Curiosity’s wheels were damaged on the rough Martian terrain, engineers strengthened Perseverance’s wheels. During landing, Perseverance will use a technology called terrain relative navigation, analyzing images as it descends to enable a more precise landing.
The rover has a new suite of instruments, including cameras and spectrometers, to study the Jezero Crater site. Billions of years ago, a river delta flowed into a lake there, and scientists believe rocks may preserve evidence of past life. “We’ll be searching for biosignatures: patterns, textures or substances that require the influence of life to form,” said Katie Stack Morgan, Mars 2020 deputy project scientist.
Perseverance also carries an experiment called MOXIE that will test a way of producing oxygen from atmospheric carbon dioxide that could be used by future human missions. Tucked underneath the rover is a tiny helicopter named Ingenuity. After landing, Perseverance will release Ingenuity and drive away, allowing controllers to test its ability to fly in the planet’s thin atmosphere.
The most important difference about Perseverance, though, is its mission to cache samples. The rover will be able to drill into rocks to collect samples about the size of a piece of chalk and weighing 15 grams, which it then will place into a sample tube.
That mechanism is remarkably complex, with the additional challenge of sterilizing the system to avoid contaminating samples with terrestrial microbes. “In terms of technology, it is the most complicated, most sophisticated mechanism that we have ever built, tested and readied for spaceflight,” said Adam Steltzner, chief engineer for Mars 2020.
Scientists will have to choose carefully: there are only about three dozen tubes available to fill with samples. “This is a finite resource, and the science teams will have to make the decision in real time: do we want to collect this rock or do we want to collect that rock?” Farley said.
MARS SAMPLE RETURN PLANNING
Caching the samples is just the beginning of Mars sample return. Yet, for much of the development of Mars 2020, there was no formal plan for returning its samples.
NASA announced in 2017 it would pursue a “lean” architecture for sample return, and since then has been slowly developing it in cooperation with the European Space Agency. “We’ve been working really hard over the last several years with ESA to develop a partnership to share the burden of the remaining two missions that it takes to bring home the samples,” said Jim Watzin, director of NASA’s Mars Exploration Program.
NASA will take the lead on the first of those two missions, a lander scheduled for launch in mid-2026. It will touch down near the Mars 2020 landing site and deploy a small “fetch” rover built by ESA. That rover will pick up the sample tubes cached by Perseverance and load them into a canister in the lander. A small rocket on the lander will launch that canister into orbit.
A second mission, led by ESA, will launch later in 2026 and go into orbit around Mars. It will carry a NASA-supplied payload to capture the basketball-sized canister and load it into a secure container. The orbiter will then use electric propulsion to leave Mars orbit and return to Earth, with the sample container landing in Utah in 2031.
Watzin says the architecture is designed to minimize the number of “pinch points,” or single-point failures, for getting samples back. For example, Perseverance will hold on to some samples it collects and will return them to the lander, offering redundancy for the fetch rover. Once launched, the sample canister will be in an orbit around Mars that should be stable for decades in case there’s a problem with the orbiter intended to bring them back to Earth.
“We tried to give ourselves flexibility as much as we could in the design of the architecture and the strategies for how we plan to operate,” he said.
Technical risk is not the only concern. Neither NASA nor ESA have yet estimated how much the overall sample return campaign will cost, beyond Mars 2020’s budget of $2.4 billion, plus $300 million for its first Martian year of operations.
Watzin said both agencies are moving “full steam ahead” on their roles, although the two future missions are still in their earliest phase of development: NASA plans a concept review in August, followed by beginning Phase A work in September. “We’re on track for a 2026 launch date.”
PERSEVERING THE PANDEMIC
First, Mars 2020 needs to get off the ground. The window for the mission opens July 17, but several issues with processing the Atlas 5 rocket have delayed the launch to no earlier than July 30. The mission has to launch by mid-August or wait until the next launch window opens in 2022.
The coronavirus pandemic, which hit shortly after the spacecraft arrived at the Kennedy Space Center for launch processing, complicated launch preparations. NASA took measures to ensure the safety of those people working on the rover at KSC or the Jet Propulsion Laboratory.
“The objective was to keep the team as safe, or safer, than they would be if they were not working,” said Wallace. “Putting a spacecraft together that’s going to Mars and not making a mistake is hard no matter what. Trying to do it during the middle of a pandemic is a lot harder.”
NASA made Mars 2020 one of its highest priorities, along with SpaceX’s commercial crew mission. “It’s very expensive if we have to take Perseverance and put it back into storage for a period of two years,” NASA Administrator Jim Bridenstine said at a June briefing about the mission. “It could cost half a billion dollars.” He didn’t elaborate on that cost estimate, and NASA Headquarters was unable to itemize the costs after several requests.
Mars 2020 carries a small plaque honoring the medical profession for their response to the pandemic. “They really inspired us, I think, through this period, and we hope that this plate, and we hope that this mission, in a small way can inspire them in return,” Wallace said.
The pandemic added a new dimension to the rover’s name. Morgan, for example, said she wasn’t that excited about “Perseverance” when NASA announced the name in early March. “I’m a convert now. Perseverance is the right name for the rover,” she said three months later. “I think it’s now a really important symbol of humanity hopefully persevering though this great challenging time.”
Mars scientists understand the value of perseverance. They’ll need plenty more perseverance over the next decade waiting for those samples of the red planet to come to Earth.
This article originally appeared in the July 13, 2020 issue of SpaceNews magazine.