01:26 - Source: CNN Business
Why NASA calls landing the Mars rover '7 minutes of terror'

Editor’s Note: Don Lincoln is a senior scientist at the Fermi National Accelerator Laboratory. He is the author of several science books for general audiences, including the best-selling audio book “The Theory of Everything: The Quest to Explain All Reality.” He also produces a series of science education videos. Follow him on Facebook. The opinions expressed in this commentary are solely his. View more opinion articles on CNN.

CNN  — 

In the depths of space, a speeding projectile races away from Earth and toward a date with destiny.

A NASA spacecraft holding a robot with the noble name Perseverance is en route to Mars. Perseverance will explore the Martian surface, tasked with looking for evidence of Martian life and collecting samples that researchers hope will one day be returned to Earth for analysis.

Don Lincoln

The discovery of life that evolved on a planet other than Earth would change humanity’s understanding of its place in the cosmos. The last time such a paradigm-shifting advance occurred was in 1610, when Galileo first saw the moons of Jupiter, proving that the Earth (and, by extension, humanity) isn’t at the center of the universe. And, since our celestial neighbor once hosted liquid water, it’s an excellent location to look for ancient life.

Exploration is what humanity does. It’s in our nature. We’ve explored our planet and one day we hope to leave Earth to first explore the solar system, and then the stars. But first we must learn how. And if Perseverance is successful and finds evidence for ancient Martian life, it will tell us something enormous about the universe waiting for us.

On Thursday, NASA engineers will send the signal that will direct the landing craft to head for the surface. This is, by far, the most dangerous part of the mission. Because Mars is currently about 200 million kilometers from Earth, it takes a radio signal over eleven minutes to travel between the planets.

But the landing sequence takes less than that – seven minutes, in fact. Thus, the process of landing on Mars has to be completely automated – done by the spacecraft itself, relying on the ingenuity of NASA’s engineers and programmers to get it right. And, as good as they are, they’ve got reason to be nervous. Only about half of the missions to Mars have landed successfully. It’s no surprise that the landing phase is called “seven minutes of terror.

Once the landing craft starts descending to the planet, an incredibly complex series of steps have to be executed correctly. First, the Martian atmosphere is used to slow the craft. A heat shield protects the delicate probe during this stage. The shield is necessary, as the temperatures during descent will rise to as much as 2,370 °F (1,300 °C).

When the craft is about 7 miles (11 km) above the surface, rocketing along at about 540 mph (865 kph), it will deploy a parachute to slow it further. Once the craft is slowed sufficiently, it will jettison the parachute and the heat shield and rockets will take over. For the last 60 seconds or so, the craft will descend slowly under rocket power, until it gets near the surface. At that point, the craft will hover and lower the Perseverance lander onto the Martian surface using nylon cords. When Perseverance is on the ground, the cords will detach, and the landing craft will then rocket off to crash far away.

This landing process sounds extremely complicated, but it’s exactly how the NASA Curiosity rover was successfully landed on Mars. Curiosity landed in 2012, and it continues to operate. Curiosity has been staggeringly successful, and NASA hopes Perseverance will have a similarly successful story.

Perseverance will land some 2,300 miles from the Curiosity rover, in the Jezero crater on Mars, which was once a river delta, disgorging into a lake. Researchers believe that if life once existed on Mars, then the place to look for it is a place that was wet and the minerals of a fossilized river delta are an ideal vault to store the evidence.

Two of Perseverance’s other goals are to study the weather and geology of the Martian surface, but it is also tasked with a fourth mission of making measurements that will help scientists and engineers plan for future manned missions.

Perseverance is also the first rover designed to collect and preserve samples of rock, which will hopefully one day be returned to Earth. The current spacecraft cannot accomplish this. It will have to wait for a possible future mission. This second mission, if it occurs, is scheduled for 2026, with an earliest return date of 2031.

In addition to Perseverance’s main missions, the probe also contains what is called a “technology demonstration mission.” This is the Ingenuity Mars Helicopter. This helicopter weighs about four pounds (1.8 kg) and it’s very similar to a drone like one you might fly from your backyard. The small and autonomous probe is the first example of a device that will fly in the thin Martian atmosphere. The probe will help researchers decide which directions to send the Perseverance rover to explore.

While the primary mission of Perseverance will last a Martian year (687 Earth days), if the Curiosity rover is any example, Perseverance might operate for a decade, collecting a treasure trove of data. If the landing sequence is successful, Perseverance will add a great deal to our understanding of the Martian environment and may provide the first evidence for ancient Martian life.

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    While the Perseverance probe is a very exciting one, it’s not the only one slated to arrive at Mars. Two other probes were also launched around the same time. One was the Chinese Tianwen-1 probe which, if successful, will land a rover on the Martian surface in perhaps May or June. This will make China the second country to successfully land a rover on Mars. (The Russian Mars 3 mission in 1971 landed, but failed less than two minutes after touching the Martian surface and after sending a single gray image. The Tianwen-1 orbiter entered Martian orbit on February 10.

    In addition, the United Arab Emirates sent a Martian orbiter probe, with the name of Hope. This orbiter arrived at Mars on February 9.

    Let’s hope that NASA chalks up another mark in the win column. I know that I’ll be holding my breath during those seven scary minutes.