Perseverance Arrives on Mars – Sky & Telescope


Mars has welcomed its newest emissary from Earth, as NASA’s Perseverance rover plopped onto the planet’s surface today at 3:55 p.m. Eastern Standard Time (20:55 Universal Time).

Its arrival inside Jezero crater followed a perilous 7-minute descent through the planet’s thin atmosphere. In the time it takes to brew a pot of coffee, an aerodynamic shield, parachute, and rockets reduced the arriving spacecraft’s velocity from 5.4 kilometers per second (12,100 mph) at the top of the Martian atmosphere — 150 km (95 miles) up — to a final gentle touchdown on the frigid landscape.

Mars landing
Perseverance’s entry, descent, and landing sequence. In just 7 minutes, the spacecraft decelerated from 5.4 kilometers per second (12,100 mph) to a gentle landing on the Martian surface.
NASA / JPL

An anxious team of NASA scientists and engineers received confirmation of the successful landing from Perseverance via a pinball-like set of communication links. That’s because the rover touched down at a time when the landing site didn’t have a direct line of sight back to Earth. So first it sent a signal at ultrahigh frequencies to a receiver on NASA’s Mars Reconnaissance Orbiter (MRO), cruising high overhead. Then MRO sent the confirmation to a huge radio dish in NASA’s Deep Space Network located west of Madrid, Spain, which relayed it to the mission’s control center at the Jet Propulsion Laboratory in Pasadena, California.

Because Mars is 205 million km (127 million miles) away, the touchdown telemetry took 11m 21s to reach JPL. The time delay also forced the spacecraft’s entire entry, descent, and landing sequence to happen autonomously, without any help from the project’s team back on Earth.

This “you’re on your own” landing sequence has been the norm for every Martian orbiter or lander — and not always successfully. But Perseverance was equipped with new technologies (a range trigger that timed the parachute’s opening, and terrain-relative navigation that matched the ground below to stored imagery) to steer the spacecraft to its target as it hurtled through the atmosphere.

These are the first pictures relayed by Perseverance after its successful landing on Mars. They were taken by its forward- and backward-looking hazard-avoidance cameras. Taken through red filters, the views look hazy because the cameras are still covered by clear protective shields.
NASA / JPL

An Ambitious Mars Mission

Launched last July 30th atop a powerful United Space Alliance Atlas V rocket, Perseverance cruised across 471 million km (293 million miles) of interplanetary space over 6½ months to reach Mars. Its arrival, the most challenging ever attempted by NASA, placed the rover inside a nearly circular landing ellipse inside Jezero that’s just 7.7 km (4.8 miles) long — less than a third the size of that for the Curiosity rover, which arrived in August 2012, and just 125 the size of the ellipse targeted by Mars Pathfinder in 1997.

This pinpoint precision was essential in part to make sure that Perseverance landed inside Jezero, which is 45 km (23 miles) across. Located at 18°N, 77°E, this ancient crater is on the boundary between dark Syrtis Major Planum to its west and Isidis Planitia, a giant impact basin, to its east.

Perseverance landing site map
Perseverance landed within its planned landing ellipse, though though a bit southeast of its center. Even so, mission planners achieved the most precise landing ever attempted on Mars — aiming for a much smaller target zone than that for any of its predecessors.
NASA / JPL

More critically, mission scientists wanted the rover to land on a rugged fan of debris deposited on the crater’s floor by a river that breached the western rim. Some 3½ billion years ago, the crater walls also confined a lake that covered its floor. In fact, MRO has mapped the presence of clay minerals in and around the crater that must have formed in the presence of water.

As the image above shows, the spacecraft ended up a couple of kilometers to the southeast of the sediment-rich delta that will be “ground zero” for its explorations — easily reachable once the rover becomes mobile. Critically, it landed in a relatively flat, rock-free spot. “We landed in a parking lot,” quips Al Chen, the (very relieved) leader of the mission’s Entry Descent and Landing team.

Scientists hope that the eons-old sediments on Jezero’s floor still preserve organic molecules that will help them determine whether Mars was once inhabited. They’ll also look for clues in analyses of any clay or carbonate minerals the rover might encounter.

Perseverance is the most massive and complex spacecraft ever to reach the surface of Mars. Although it inherits much from its predecessor Curiosity, in many ways “Percy” is a much more capable spacecraft. The car-size rover has a mass of just over 1 metric ton (2,260 pounds); it’s about 3 meters (10 feet) long (not including the robotic arm) and 2.2 m (7 feet) tall. And scattered around its frame are 23 cameras for navigation, hazard avoidance, surface inspection, and (of course) taking selfies.

Perseverance will carry 23 cameras, including seven specifically for scientific purposes, and a sample-caching system, which will package and lay aside samples for a later mission to pick up and carry home. It also carries five instruments designed to explore the history of water and chemistry in the ancient lake basin.
NASA / JPL

The rover’s seven instruments are listed in the table below:

Experiment Acronym Task
SuperCam Imaging, chemical analysis, and mineralogy in rocks and regolith from a distance (an upgrade of ChemCam on Curiosity)
MastCam-Z Stereoscopic imaging, equipped with zoom lens
Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals SHERLOC Ultraviolet spectrometer that uses imaging and an ultraviolet laser to determine fine-scale mineralogy and detect organic compounds
Planetary Instrument for X-Ray Lithochemistry PIXL X-ray fluorescence spectrometer to determine the elemental composition of Martian surface materials
Radar Imager for Mars’ subsurface experiment RIMFAX Ground-penetrating radar to image different ground densities, structural layers, buried rocks, meteorites, underground water ice, and salty brines to depths of 10 m (33 feet)
Mars Environmental Dynamics Analyzer MEDA Measures temperature, wind speed and direction, pressure, relative humidity, radiation, and dust particles’ size and shape
Mars Oxygen ISRU Experiment MOXIE Technology test to produce oxygen (O2) from atmospheric carbon dioxide (CO2).

Some aspects of these investigations have been standard equipment on recent rovers, but SHERLOC is a crucial addition that’s specifically designed to detect organic molecules.

Apart from the rover’s suite of sophisticated instruments, it has two additional roles that are sure to grab headlines. One is that, over time, the rover will collect surface samples, seal them in specially designed tubes about the size of an index finger, and then deposit the tubes at a cache site so they can be retrieved and returned to Earth by future spacecraft.

The second innovation — and one I’m especially keen to see in action — is the Ingenuity Mars Helicopter. Weighing just 1.8 kilograms (4 pounds), it’s a small, “autonomous rotorcraft” (a.k.a. a drone) designed to test powered, controlled flight in the thin Martian atmosphere. Ingenuity carries a camera but no instruments, because its objective is simply to fly successfully. Public interest in this little whirligig is so high that NASA decided to give Ingenuity its own “press kit.”

For now, the engineering team will carefully check out Perseverance to make sure all systems are functioning correctly. Expect to see some panoramas of the rover’s surroundings in the coming days. But the real science won’t begin until roughly three months from now.

If you want all the facts and figures about Perseverance, its flight to Mars, how it landed, and what explorations are planned, check out this 72-page press kit.

NASA’s Mars 2020 mission (as this effort is collectively known) reached the Red Planet just days after the arrivals of the United Arab Emirates’ Hope orbiter and China’s Tianwen 1, which will soon dispatch its own rover to the surface. If that landing is successful, then the census of current operational Martian spacecraft (including the ones pictured below) will be eight orbiters and four rovers/landers. It’s an amazing time for Martian exploration!

Mars missions in 2020
Before the new arrivals, Mars already hosted a fleet of craft, including NASA’s Insight lander and Curiosity rover as well as six orbiters: India’s Mars Orbiter Mission, the European Space Agency’s ExoMars Trace Gas Orbiter and Mars Express missions, and NASA’s Mars Odyssey, MAVEN, and Mars Reconnaissance Orbiter.
Gregg Dinderman / S&T / PE3K / shutterstock.com





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