The U.S. space agency’s Perseverance rover is now just three weeks from arriving at Mars.
The robot’s current distance to the Red Planet is still about 4.5 million km (3 million miles), but the gap is widening rapidly.
The largest, most sophisticated vehicle ever sent to another planet, the Nasa robot is aimed at an almost equatorial crater called the Jezero.
Touchdown is expected on Thursday 18 February shortly before 2100 GMT.
To get off, the Nasa rover will have to survive what engineers call the ‘seven minutes of scare’ – the time it takes to get from the top of the atmosphere to the surface.
The ‘terror’ is a reference to the frightening challenge inherent in the attempt to reduce an access speed of 20,000 km / h to something like walking at the moment from ‘wheels’.
‘When scientists look at our landing site, Jezero Crater, they see the scientific promise of everything: the remains of an ancient river flowing in and out of this crater, thinking it’s the place to look for signs of past lives. But when I look at Jezero, I see danger, ‘says Allen Chen, the engineer who leads the effort, descent and landing effort for perseverance.
“There was danger everywhere. There is this 60-80 meter long cliff that cuts right through our landing area. If you look to the west, there are craters where the rover can not get out, even if we were to land successfully. In one of “And if you look to the east, there are huge rocks that our rover would be very unhappy about if we put them down,” he told BBC News.
Fortunately, Perseverance has some proven technologies that should ensure that it reaches a safe point on the surface. Among them is the famous “Skycrane” jet suit that successfully landed Nasa’s previous robber, Curiosity.
There are even some add-ons designed to improve reliability. The parachute system that slows down the atmospheric descent from super- to sub-sonic velocities now has something called a ‘series trigger’. It is more accurate opening the parachute to bring the rover closer to its popular bulls-eye.
Unlike curiosity that has just opened the gutter when it has reached a predetermined velocity, perseverance will first check its surroundings before the command is issued.
Related to this is Terrain Relative Navigation. Perseverance will examine the ground below and examine it using satellite images of the crater to better determine its position.
It’s like me or you looking out the window of our car and then looking back at a map to see where we are, Chen says.
“This is what we ask Perseverance to do on its own, to find out where she is, and then fly to well-known safe places in the area.”
Curiosity managed to get about a mile away from the fictional eye. It left slightly. Perseverance, with its improved landing technologies, should do much better.
Scientists have already named the area with the bulls-eye. It is called Timanfaya, named after the Spanish National Park in Lanzarote, one of the Canary Islands.
The Lanzarote Timanfaya is a volcanic site; the Mars version, which includes a square of 1.2 km by 1.2 km, probably also has volcanic rock. This is the floor of the Jezero crater.
Although it is the landing site, it is not of the utmost importance for the mission. It is the remaining delta in the north, along with some distant carbonate rocks that, according to the researchers, could trace the edge of a once huge lake in Jezero.
“Carbonate rock is very common on Earth, but is very rare on Mars and we do not really know why it is,” said Ken Farley, a scientist at the Nasa Project on Perseverance.
“There is an area at the edge of the crater that would have been the shore with a high concentration of carbonate. It is very attractive to us, because on earth carbonate is often precipitated [by living organisms]: people will be familiar with things like coral reefs. “It’s a great way to record bio-signatures,” he told BBC News.
The dream is that perseverance over fossil evidence of stromatolites will stumble. These are sedimentary deposits formed by layers, or mats, of microorganisms.
The structures and the chemistry in them are recognizable to geologists. That said, we are talking about rocks in Jezero that are almost four billion years old.
Discoveries are probably not of the slam-dunk variety, and therefore endurance will pack the most interesting finds for later missions and bring them back to earth for more detailed study.
Farley says perseverance will ask the most important questions and answers it will provide.
“Is this a case of if you build a habitable environment, then life will come? Or is it like a magic spark that must happen too? And the answer to that question is really important, because we now know that there are billions is, literally billions of planets out there on earth.
“What is the probability that life does not exist there? It seems small to me, but it all depends on how common is the spark that life gets going on,” he explained.
Originally published