NASA Lands Its Perseverance Rover on Mars
The spacecraft’s journey to the red planet was a success, extending the American record of safe landings there to six.
NASA landed a new robotic rover on Mars on Thursday, its most ambitious effort in decades to directly study whether there was ever life on the red planet.
While the agency has landed other missions on Mars, the $2.7 billion robotic explorer named Perseverance carries a sophisticated set of scientific tools that will bring advanced capabilities to the search for life beyond our planet.
Perseverance was the third robotic visitor from Earth to arrive at the red planet this month. Last week, two other spacecraft, Hope from the United Arab Emirates and Tianwen-1 from China, entered orbit around Mars.
But NASA’s spacecraft did not go into orbit first. Instead it zipped along a direct path to the surface.
At 3:48 p.m. Eastern time, controllers at the mission operations center at NASA’s Jet Propulsion Laboratory near Pasadena, Calif., received word from Perseverance that it had entered the top of the Martian atmosphere at a speed of more than 12,000 miles per hour. The spacecraft was beginning the landing maneuvers that would bring it to a soft stop in just seven anxiety-drenched minutes.
All that anyone on Earth could do was watch and hope that Perseverance performed as designed. At Mars, the fate of the rover was already determined.
Mars is currently 126 million miles from Earth. Radio signals, traveling at the speed of light, take more than 11 minutes to travel from there to here. That means that when the message announcing the start of the landing sequence reached Earth, the rover had already been on Mars for four minutes. The only uncertainty was whether it was safe there in one piece, or crashed into many pieces, another human-made crater on the surface of Mars The atmosphere of NASA’s operations center — more sparsely filled than previous Mars landings because of precautions required by the coronavirus pandemic — was pensively quiet.
There were periodic announcements of the spacecraft’s progress through the atmosphere: the deceleration and heating as it sliced through the thin Martian air, the deployment of a huge parachute even as it was still supersonic in speed, the shedding of the rover’s heat shield so that its cameras could navigate to its destination, the firing of rocket engines to further slow its descent.
In the final step, the rover was lowered at the end of a cable beneath a rocket-powered jetpack until it touched the surface.
At 3:55 p.m. cheers erupted in the control room as a member of the mission control announced that Perseverance was intact on the surface.
In a nutshell, Perseverance had to decelerate from more than 12,000 miles per hour to a full stop during what NASA calls “seven minutes of terror,” for the period of time from the rover’s entry into the atmosphere until its landing. There was no chance for a do-over. The path of Perseverance intersected with the surface of Mars. The only question was whether the rover ended up in one piece, ready to begin its mission, or smashed into many pieces.
The thin atmosphere of Mars adds several levels of difficulty. A spacecraft needs a heat shield, because the compression of air molecules heats its bottom side to thousands of degrees. But there is not enough friction to slow it down for a gentle landing with just parachutes.
The spacecraft had to handle the landing operation all by itself. It takes 11 minutes for a radio signal to travel from Mars to Earth. That means if anything went wrong, it would already be too late by the time people in NASA’s mission operations center got word.
“It all has to happen autonomously,” said Matt Wallace, a deputy project manager. “Perseverance really has to fight her way down to the surface on her own. It’s something like a controlled disassembly of the spacecraft.”
About 80 seconds after entering the atmosphere, the spacecraft experienced peak temperatures, with the heat shield on the bottom of the capsule reaching 2,370 degrees Fahrenheit. Inside the capsule, it’s a lot less toasty — about room temperature. As the air became denser, the spacecraft continued to slow.
Small thrusters on the top of the capsule fired to tweak the angle and direction of its descent and keep it on course toward its landing site.
At an altitude of about seven miles, four minutes after entry into the atmosphere, the capsule was traveling at a speed under 1,000 miles per hour. It then deployed a huge parachute, more than 70 feet in diameter.
The spacecraft next dropped its heat shield, allowing cameras and other instruments to take note of the terrain below to determine its position.
Even with the huge parachute, the spacecraft was still falling at about 200 miles per hour.
The next crucial step was called the sky crane maneuver. The top of the capsule, called the backshell, was let go and is carried away by the parachute. There were two pieces of the spacecraft left. The top was the descent stage — in essence a rocket-powered jetpack carrying the rover beneath it. The engines of the descent stage fired, first steering to avoid a collision with the backshell and the parachute. Then the engines slowed the descent to less than two miles per hour.
About 66 feet above the surface, the rover was then lowered on cables. The descent stage continued downward until the wheels of the rover hit the ground. Then the cables were cut, and the descent stage flew away to crash at a safe distance from the rover.
NASA has done this before. The Curiosity rover, which is currently on Mars, successfully used the same landing system in 2012.
“We’ve never really come up with a good way of calculating the probability of success,” said Mr. Wallace, the deputy project manager.
Over the decades, NASA has succeeded in eight of nine landing attempts on Mars. The only failure was the Mars Polar Lander in 1999. (Two basketball-size probes carried by that mission that were released during descent and designed to survive impact also did not work.)
Over the past 20 years, NASA has gradually asked more complex questions about Mars. First, the mantra was “Follow the water,” as that is where there once may have been life. With giant canyons, winding river channels and signs of dried-up lakes, it has been clear that in the past, water has flowed on Mars even though the planet is cold and dry today.
NASA’s Perseverance rover will attempt to land in Jezero Crater, an ancient Martian lake roughly the size of Lake Tahoe. If successful, the rover will spend years exporing the river delta and making its way to the crater rim.
By Jonathan Corum | Image by NASA, Jet Propulsion Laboratory, European Space Agency, German Aerospace Center, Freie Universität Berlin and Justin Cowart. Inset image by NASA and J.P.L.
Perseverance’s destination is Jezero Crater. The rover will explore the delta of a river that once flowed into a lake that filled the crater. The piles of sediments are a promising place where the fossil chemical signatures of ancient Martian microbes might still be preserved today.
The NASA mission includes Perseverance, a 2,200-pound rover, and Ingenuity, an experimental Mars helicopter.
The four-pound aircraft will communicate wirelessly with the Perseverance rover.
Four carbon-fiber blades will spin at about 2,400 r.p.m.
The plutonium-based power supply will charge the rover’s batteries.
Instruments will take videos, panoramas and photographs. A laser will study the chemistry of Martian rocks.
Will identify chemical elements to seek signs of past life on Mars.
The aircraft will communicate wirelessly with the rover.
The plutonium-based power supply will charge the rover’s batteries.
Instruments will take videos, panoramas and photographs. A laser will study the chemistry of Martian rocks.
Will identify chemical elements to seek signs of past life on Mars.
Flying on Mars is not a trivial endeavor. There is not much air there to push against to generate lift. At the surface of Mars, the atmosphere is just 1/100th as dense as Earth’s. The lesser gravity — one-third of what you feel here — helps with getting airborne. But taking off from the surface of Mars is the equivalent of flying through air as thin as what would be found at an altitude of 100,000 feet on Earth. No terrestrial helicopter has ever flown that high, and that’s more than twice the altitude that jetliners typically fly at.
NASA’s engineers used a series of materials and computer technology advancements to overcome a number of these challenges. About two months after landing, Perseverance will drop off the helicopter from its belly, and Ingenuity will attempt a series of about five test flights of increasing duration.
If the tests succeed, it could pave the way for future, larger Marscopters. Having the option of using robotic fliers could greatly expand a space agency’s ability to study the Martian landscape in more detail, just as the transition from stationary landers to rovers did in earlier decades.
Send a robotic spacecraft to Mars, grab some rocks and dirt and bring those back to Earth.
It’s more like an interplanetary circus act than you might imagine, but NASA and the European Space Agency think that now is the time they can finally pull off this complex choreography, tossing the rocks from one spacecraft to another before the samples finally land on Earth in 2031.
One of the key tasks of Perseverance is to drill up to 39 rock cores. Each sample of rock and dirt, weighing about half an ounce, will be sealed in an ultraclean cigar-size metal tube, and Perseverance is to drop each tube back on the surface.
Under current plans, the samples will wait in the cold as the rover continues its studies of Jezero crater.
Two spacecraft are to blast off to Mars in 2026 as part of a mission to bring the rocks back.
Waiting above Mars for the sample container, about the size of a soccer ball, will be the Earth Return Orbiter, built by the European Space Agency. Assuming it captures the container successfully, the orbiter would then depart Mars. As it approached Earth, it would eject the samples, which will land in the Utah desert.
The mission is expected to cost several billion dollars, but this is a long-sought goal of Mars scientists, to closely study rocks and see if they discern whether life once existed on Mars.
“To really get into some of the really intriguing questions at a detail level means we need to parse the evidence down on the molecular level and try to tease the information out of very, very old material,” James Watzin, the director of the Mars exploration program at NASA, said in an interview in 2020. “And that requires a whole suite of instrumentation that was clearly too large to shrink and send to another planet.”
NASA’s rover is the third spacecraft to arrive at the red planet this month. Two more robotic probes, built by the United Arab Emirates and China, went into orbit last month. All three spacecraft launched in July 2020, aiming to take advantage of the period every two years when the journey between Earth and Mars is shorter than usual.
But the Hope spacecraft will also aid planetary scientists on Earth. During its mission of at least two years, it will collect data on how dust storms and other weather conditions near the surface affect the speed at which Martian air leaks into outer space. This could help further understanding of how Mars, a world that had running water on its surface in the early days of the solar system, turned into the cold and seemingly lifeless world that it is today.
Whether or not Perseverance sticks its landing on Thursday, it won’t be the only spacecraft to attempt to touch down on Mars in one piece this year.
In addition to the new arrivals, six more orbiters are currently studying the planet from space. Three were sent there by NASA: Mars Odyssey, launched in 2001, Mars Reconnaissance Orbiter, launched in 2005, and MAVEN, which left Earth in 2013.
Europe has two spacecraft in orbit. Its Mars Express orbiter was launched in 2003, and the ExoMars Trace Gas Orbiter lifted off in 2016 and is shared with Russia’s space program.
India operates the sixth spacecraft, the Mars Orbiter Mission, also known as Mangalyaan, which launched in 2013.
Two American missions are currently operating on the ground. Curiosity has been roving since 2012. It is joined by InSight, which has been studying marsquakes and other inner properties of the red planet since 2018. Another American mission, the Opportunity rover, expired in 2019 when a dust storm caused it to lose power.
While Mars is a highlight of NASA’s calendar this year, it has many other interesting missions planned in the months to come. While some may slip into 2022 for a variety of reasons, others are likely to get off their launchpads this year.
NASA also has a number of missions to the moon that could occur this year.
The agency is also scheduled to launch two other missions into deep space in 2021.
Category: Science
Source: New York Times