Thursday , April 22 2021

Journey to the heart of the red planet to hear your vital signs

"It is good to renew our capacity for admiration," said the philosopher, "the interplanetary journey has given us back to childhood."

The phrase, which precedes a traditional edition of Ray Bradbury's classic
Chronicles(Minotauro, 1976, prefigured by Borges), it is very appropriate to wait for the ineffable encounter that will take place today in the vastness of space. At 5 pm local time, after traveling for more than six months, NASA's Insight probe will land on the Martian surface to begin a two-year ground mission that will allow us to understand the processes that shaped Earth's rocky planets. Solar System (Mars itself, Venus, Mercury and also Earth), 4,500 million years ago.

"It is a static ship, not a rover, like Viking," explains the experienced Argentine engineer Miguel San Martín, who, after directing four successful descents in our cosmic neighbor, is part of the group of advisors who supervised the project and the So far, most probes and satellites have focused on studying the surface and finding out if there is or has ever been life on Mars, it has nothing to do with this, but with the exploration of the interior: The Red Planet does not have a powerful magnetic field like Earth, which is critical to protect the atmosphere from the solar wind. "

"Why did you miss it?" It's a mystery, on the other hand, the Earth is such an active planet that the evidence of its formation is already contaminated, while there, where things are not so dynamic, we can analyze them better. It's like studying the Earth's past on Mars and understanding why they differentiated, "he adds.

The planets of the Solar System were formed from a disk of rocks, ice and debris orbiting around our home star. Mars is by far the most studied after Earth, but astronomers know practically nothing of their interior. So far, the multiple missions that have taken place since NASA sent its first orbiter in 1971, Mariner 9 (which returned 7300 images of its surface and its two moons, Phobos and Deimos) analyzed its atmosphere, recorded its dust storms and sought (without success) signs of life.

With the launch originally planned for 2016, which should have been postponed due to a vacuum leak in one of the landing module equipment, Insight (corresponding to "Internal Exploration using Seismic Investigation, Geodesy and Heat Transport")) has three main instruments.

A seismograph will hear small vibrations from the ground, from fractions of nanometers (billionth of a meter), due to seismic waves that travel the planet and that will allow to create a 3D image of its interior.

A drill drill about five meters from the Martian crust to analyze the heat coming from the depths and this gives you an idea of ​​its activity. And another experiment will try to determine very precisely how much the Martian north pole is "shifted" as it orbits the Sun. These observations will provide detailed information about the size of the iron-rich core of Mars and help determine whether it is liquid and that others contain elements .

"The most interesting thing about these missions is that they allow us to better understand our world," says Diego Bagu, an astronomer at the National University of La Plata and director of the Planetarium in the city. "This is the first time we are going to be able to drill the Martian soil and find out if it has seismic movements and how the heat flow is, even if it does not have a fractured crust like the Earth presents and therefore there is no plate movement tectonics, there may be geological activity due to the impact of meteorites, for example, studying how seismic waves propagate will allow us to know what the interior of the planet is like. "

Seven minutes of terror

Once you arrive at your destination, Insight will perform one of the crucial steps of the entire mission: deploy your solar panels. Thus, about one meter high and 360 pounds in weight, it will reach six meters in length (equivalent to half to two thirds of the length of a collective). With these "wings" you can capture the sun's rays (which at this distance shine 50% less than on Earth) to power the instruments.

Unlike other probes, you'll need to use an articulated robotic arm to slowly put instruments on the surface, a process that will take about three months.

But for all of this to happen, you first have to overcome the "inlet, descent, and landing" (EDL) sequence, an operation that causes adrenaline to flow into the control center because, although it has been repeated, it is not absolutely guaranteed.

"While Insight is an almost identical copy of the 2007 Phoenix, and we know the design is solid, there can always be a workforce error," argues San Martin, a veteran of those laws. but sometimes something happens to us.The atmosphere of Mars varies according to the seasons as it happens here.The pressure can increase or decrease.When it is less dense, the landing becomes more complicated.And there may also be storms of dust. For this reason, a team from NASA's Jet Propulsion Laboratory (JPL) followed the approach trying to make a prediction for the crucial moment, because in theory, the descent system parameters could be changed to make it more robust. Opportunity, for example, we had a disturbed atmosphere and we made small adjustments to maximize the chances of success, "he adds.

In fact, at the last moment of yesterday, the Insight team decided to run the last fix on the trajectory to move the landing point for about 16 km.

In addition, there are other obstacles. In order for the ship to descend properly, it must enter the correct angle: if it is too steep, it may be incinerated; if, on the contrary, it is very open, it will leave the atmosphere and remain floating in space.

"In about six and a half minutes, the module will go from a speed of almost 20,000 km per hour to eight," says Bagu, "and he needs to enter through a window of 10 km by 20 on each side, an area smaller than one City".

Although the atmosphere of Mars is 100 times thinner than the Earth's atmosphere, at the entrance the module must be protected from friction with a heat shield prepared to withstand more than 1300 ° C. Then it will implant its parachute and, approximately 40 seconds before coming into contact with the ground, it will release, extend its legs and light 12 thrusters to slow down and land in an area known as Elysium Planitia, chosen because it is dusty. and flat and relatively rock-free.

Marco Polo on Mars

Another innovation of this mission is that the probe travels with two minisatellites (or
cubes) of the approximate size of a shoebox, MarCO-A and MarCO-B (which mission technicians call Marco / Polo), which will be responsible for providing ground-based communication services as the module continues to execute stage after stage of landing, and are a proof of concept to be used in the exploration of interplanetary space.

"In 1999, a ship told us" chau, we see ourselves on the surface "and we never hear of it again," says San Martin, "then NASA stipulated that each descent should have telemetry so that if it fails , we can determine what did not go well and fixed in later trips. Normally, we have spaceships that are in orbit and that make us
retransmission. Insight carries these two
cubes which separated after the launch and goes flying in parallel, but behind. During the landing, these small satellites will receive the signal and send it to Earth. And the good thing is that if it works, we will not have to worry that there's always a satellite alive – on Mars in the correct geometry for landing. "

Contrary to what one might think, the international success rate on the decks is not high, around 40%. "Sometimes it seems like these things are already routine," Bagu concludes, "but in reality they are an extraordinary challenge."

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