NASA's Mars probe arrives Monday after seven minutes of terror.


An illustration of NASA InSight lander drilling on the surface of Mars. (NASA via AP)

The endless stretch, from the moment a spacecraft reaches the Martian atmosphere to the second that touches the rusty surface of the Red Planet, is what scientists call the "seven minutes of terror."

To land a spacecraft on Mars is as difficult as it seems. More than half of all missions do not safely reach the surface. Because it takes more than seven minutes for light signals to travel 100 million kilometers to Earth, scientists have no control over the process. All they can do is program the spacecraft with its best technology and wait.

The seven-minute terror of InSight, NASA's newest Mars explorer, begins on Monday shortly before 3:00 p.m. Eastern Time. It is the first mission to study seismic waves on another planet; By probing the interior of Mars, scientists aim to uncover signs of tectonic activity and clues about the planet's past.

But first they need to get there.

Around 2:47 pm Monday, engineers at the Jet Propulsion Laboratory will receive a signal that InSight has entered the Martian atmosphere. The spacecraft will plummet to the surface of the planet at a rate of 12,300 miles per hour; within two minutes, the friction will have baked its heat shield at a temperature of 2,700 degrees Fahrenheit. In another two minutes, a supersonic parachute will be used to help the spacecraft to slow down.

From there, the most critical descent checklist unfolds into a quick clip: 15 seconds to separate the thermal protector. Ten seconds to implant the legs. Turn on the radar. Release the back shell. Shoot the retrorsockets. East for the landing.

Assuming that everything goes well, at 12:01. scientists will hear a small beep – a signal that InSight is active and functioning on the Red Planet.

This photograph taken by the Mars Odyssey orbiter shows the target landing site of NASA's InSight module in the Elysium Planitia region on Mars. (PHOTO AFP / NASA / JPL-Caltech / ASU)

The goal is to determine what Mars is made of and how it has changed since it formed more than 4 billion years ago. The results could help solve the mystery of how the Red Planet has become the dry, desolate world we see today.

Early in its history, Mars may have looked a lot like Earth. Magnetization in ancient rocks suggests that it has a global magnetic field like Earth's, fed by a stirring mantle and a metal core. The field would have shielded the planet from radiation, allowing it to cling to a much thicker atmosphere than it does today. This, in turn, probably allowed liquid water to accumulate on the surface of Mars; images of satellites reveal the contours of lakes, deltas and canyons carved by the river.

But the last 3 billion years have been a slow-moving disaster for the Red Planet. The dynamo died; the magnetic field faltered; water evaporated; and more than half the atmosphere was ripped apart by solar winds. The InSight mission is designed to find out why.

While InSight makes its precarious descent, NASA can get almost real-time information about its status through the MarCo satellites – tiny twinned experimental spacecraft known as CubeSats that accompanied InSight on its flight to Mars. Each has solar panels, a color camera, and an antenna to transmit communications from the Martian surface back to Earth.

If satellites are successful, they can provide "a possible model for a new type of interplanetary communication relay," said Anne Marinan, systems engineer. NASA Press Release.

Even without the MarCo spacecraft, NASA should know if the probe's solar arrays were installed on Monday night, thanks to recordings of the Mars Reconnaissance Orbiter. Within a day, the agency will have its first images of the spacecraft landing site – a vast, flat and almost inexpressive plain near the equator known as Elysium Planitia. This is where science will start.

Unlike Opportunity and Curiosity, the robots that run through Mars in search of interesting rocks, the InSight is designed to sit and listen. Using their dome-shaped seismic sensor, scientists hope to detect minor tremors associated with meteorite impacts, dust storms and marsquakes generated by cooling the interior of the planet. As seismic waves propagate, they will be distorted by changes in the materials they encounter – perhaps feathers of molten rock or reservoirs of liquid water – revealing what is beneath the surface of the planet.

InSight also has a drill capable of digging 16 feet – deeper than any Mars instrument before. From there, it can carry the temperature of Mars to determine how much heat is still flowing out of the planet's body. Meanwhile, two antennas will precisely trace the location of the probe to determine how much Mars rocks as it orbits the sun.

InSight insights will not only add to what we know about Mars. They could provide clues to the things that happened on Earth, billions of years ago. Most records of Earth's early history were lost due to the inexorable turnover of tectonic plates, explained Suzanne Smrekar, the mission's deputy principal investigator.

"Mars gives us the opportunity to see the materials, the structure, the chemical reactions that are close to what we see inside the Earth, but it is preserved," she said. "It gives us a chance to go back in time."

See More Information:

Next stop, Mars: Inside the debate about finding life on the Red Planet

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Mars: a virtual reality tour of the Red Planet


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