Is curiosity still on Mars?

Landing on Mars is imminent : The last dangerous travel stage of the NASA robot "Perseverance"

The landing maneuver of Mars missions is sometimes referred to as “seven minutes of horror”. During this time, probes that shoot into the planet's atmosphere at almost 20,000 kilometers per hour have to slow down to zero - gently. Seven minutes in which a lot can happen and millions of years of preparation could suddenly be ruined. Seven minutes in which no one can intervene if it threatens to go wrong.

Experts at the US space agency Nasa, but also in partner institutes abroad, such as in Berlin, have to endure these seven minutes this Thursday.

The “Perseverance” rover, launched in summer 2020, is on its way to the Jezero crater. The vehicle in small car format is to examine the soil and rock there, search for signs of primeval life, collect samples that could be brought to earth in the future and, last but not least, prepare astronautical missions to the Red Planet.

Touchdown in the Jezero crater

There is also a drone that will fly in the extremely thin Martian atmosphere and thus demonstrate the first controlled flight on another planet. Perseverance marks the beginning of a new phase in the exploration of Mars, said Thomas Zurbuchen, NASA's science director, on Tuesday. The selected crater is the most demanding landing site that has been selected so far. "There is no guarantee that the landing will be successful."

So far, on average, every second attempt to land has failed, although NASA has managed it exceptionally well in recent years. Her masterpiece so far was to drop the rover “Curiosity” (curiosity) safely in the Gale crater in 2012. Perseverance is very similar to it and is only slightly heavier at 1025 kilograms. Therefore, the same landing system was chosen to successfully cope with the seven minutes of horror.

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After the space probe has reached the Martian atmosphere at 9:38 p.m. Central European Time, the thin air alone will slow down. The heat shield will get up to 1300 degrees Celsius. At 9:42 p.m. the supersonic parachute will deploy and the heat shield will be thrown off. This gives the radar and cameras a clear view downwards. Your recordings should be compared with the programmed maps of Mars. A newly developed autopilot system analyzes the landing sites that are now possible in real time and compares them with the current position of the spacecraft in order to then determine the final landing site on the surface of Mars.

The parachute is dropped about two kilometers above the ground and landing engines ignite. The “Sky Crane” is activated at a height of 20 meters: the rover unfolds its six wheels and is lowered on nylon ropes by the floating “sky crane”. If it reports ground contact, the ropes are cut and the crane flies away a little with the rest of the thrust so that the Perseverance does not crash onto the chassis.

If all goes well, the rover will be in the Jezero crater at 9:45 p.m. Since the radio waves currently need eleven minutes to reach Earth, the redeeming signal is not expected before 9:55 p.m. With hundreds of researchers involved and costs of two and a half billion dollars, a crash landing would be a fiasco.

Stowaways undesirable

If the maneuver succeeds, Perseverance will soon send the first images and sound recordings of the landing. Then the geology robot begins its exploration of the crater. The dent in the planet's surface is 3.5 billion years old. In the past there was probably water in it, a lake about the size of Lake Constance. In addition, there were probably two tributaries with typical sediment compartments, so-called deltas. The researchers suspect that this, in the alluvial material, could also contain remains of simple living beings. Because billions of years ago the climate on Mars was more life-friendly, similar to that on young earth. It is quite possible that there was life on our neighboring planet.

But how can these “biosignatures” be found today? Experts are looking for examples on earth, reports Nicole Schmitz from the Berlin Institute for Planetary Research at the German Aerospace Center, which is involved in the mission. In Australia, for example, NASA colleagues examined bacterial mats, so-called stromatolites, both primeval, which have long been petrified, as well as those that are active today. "This is how you learn what to look out for and what the measuring devices should detect."

This is how Perseverance will proceed with its equipment. His cameras will characterize the landscape, take close-ups of finely stratified sediments and use various spectrometers to analyze the chemical and mineralogical composition of the Martian soil. “In the end, it can only be a chain of clues that provide clues to prehistoric life,” says the scientist. She is skeptical that this will be possible on site. It is more likely that samples have to be brought to earth, where there are better analytical devices in laboratories. "Presumably only these can give clear information about whether it is remnants of living matter or ordinary Mars sediment."

The rover is prepared for this. It is supposed to drill up to 20 centimeters deep and store samples that a future mission can bring to earth. Nasa and Esa are currently discussing how the transfer will work and who will pay how much. The time could come in 2031, announced Zurbuchen. Perseverance has 38 containers on board for this. "They are probably the cleanest objects there are," says Adam Steltzner, Perseverance chief engineer at NASA's Jet Propulsion Laboratory. Under no circumstances should evidence of life on Mars turn out to be remnants of terrestrial bacteria that were still stuck in the container.

It is important to avoid accidentally bringing biomass from Earth to Mars. "Precautions are taken very carefully," says Schmitz. That starts with the selection of the landing site. In order to avoid contamination, the rover may not even land where there is still running water. The researcher explains that great attention was paid to cleanliness during assembly. Every conceivable component was sterilized several times, all employees had to pass through several locks and wear special protective clothing that only leaves their eyes exposed. One hundred percent protection, as Schmitz also says, cannot exist.

Visit to the neighbor

The danger increases the more missions reach the surface of Mars. He is a popular destination. Just a few days ago two more probes arrived on the planet. On February 9, the “Al-Amal” (Hope) probe of the United Arab Emirates went into orbit. They have thus successfully completed their first interplanetary mission. Al-Amal is supposed to closely observe the weather on Mars, the interplay of the various layers of the atmosphere and wind, clouds and dust.

Shortly afterwards, on February 10th, the Chinese mission "Tianwen-1" (question of heaven) entered a Mars orbit. After a previous Mars probe was unable to leave Earth orbit while flying on a Russian rocket, China started its own Mars project and has now successfully brought a probe there. The exciting part is yet to come. The plan is to drop a rover on the “Utopia Planitia” level in May. The rover is supposed to examine the Martian soil for around 90 days on Mars and determine the distribution of water ice. The Chinese experts use the experience they have gained with robotic vehicles on the moon.

The “ExoMars” rover of the European space agency Esa was supposed to reach Mars in March. Among other things, he carries a drill that is supposed to retrieve and analyze samples from a depth of up to two meters. Down there, so the researchers hope, evidence of primeval life, protected from radiation, could have survived to this day - provided the red planet was actually animate. But the ExoMars mission already has an eventful history with several setbacks behind it. For example, the landing system caused problems and the parachute broke during tests. For these reasons and because the corona pandemic put the preparations under additional pressure, Esa and its partner Roskosmos decided in March 2020 to postpone the start planned for summer. It should now take place between August and October in 2022.

The two-year cycle is related to the orbits of Earth and Mars around them. Only every two years are the two planets in a favorable constellation to reach the other with relatively little fuel. Flights at other times would be more expensive.

This rhythm also applies to astronautical missions. They are not available for a return trip for less than two years. When it will happen is still open. Nasa remains vague with a reference to the "mid-2030s". Elon Musk is also building a rocket that is supposed to do this, called "Starship". Most recently, a test flight up to an altitude of ten kilometers was successful with the upper level, but the landing failed. It will probably take a while.

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