Today marks a milestone in NASA's mission of perseverance to Mars. At 1:40 p.m. Pacific time today, the rover will have traveled 146.3 million miles (235.4 million km). That means the spaceship is halfway to Mars and meeting with the Jezero crater. The spaceship is not moving in a straight line and the planets are moving so it is not equidistant from both planets.
"Even though we are halfway to Mars, the rover is not halfway between the two worlds," Kangas explained. "In a straight line, the Earth is 42.7 million kilometers behind Perseverance and Mars 28.8 million kilometers."
But today is still a good time to take another look at Jezero Crater and why NASA chose it as the mission's destination.
The Perseverance rover has four general goals. The two most important are finding environments that may have supported microbial life in the past and finding evidence of that life. The other two goals are to cache samples for later return to Earth for another mission and to test oxygen production from the Martian atmosphere in anticipation of future human missions to Mars.
Jezero crater was chosen because hopefully it will be particularly good at helping the first two targets. The crater is a paleolak, which means that it was once filled with water in the distant past. It was probably several hundred meters deep and about 40 km in diameter. Researchers believe it filled with water on two separate occasions. They also think that the Jezero crater was full for a long time and that the delta took 106 to 107 years to form. The lake and the canals that fed it were so long-lived that there can be up to 1 km of sediment on the bottom.
The Jezero crater is on the edge of the Isidis Basin (or Isidis Planitia), a massive impact basin. In this MOLA (Mars Orbital Laser Altimeter) image, purple is low altitude and red is high altitude. Photo credit: By NASA / JPL / USGS – (1), public domain, https://commons.wikimedia.org/w/index.php?curid=74634265
When NASA selected Jezero Crater in 2018, the scientific case was strong. It's only gotten stronger since then. In addition to the preserved sediments and the river delta, there are five different types of rock that the rover can sample. Some of the features at Jezero are estimated to be 3.6 billion years old. This is almost the beginning of Mars' Noachian Period, which began 4.1 to 3.6 billion years ago. The Noachian is when liquid water flowed over the Martian surface and formed networks of river valleys. At that time there may have been oceans and large lakes.
Orbital image of the Jezero crater with its fossil river delta. Photo credit: NASA / JPL / JHUAPL / MSSS / BROWN UNIVERSITY
Perseverance will look for signs of ancient microbial life. There are a number of powerful scientific instruments for this. It carries a ground penetrating radar, various types of spectrometers, and a variety of cameras.
The rover is really a collection of multiple robots working together. One of these is the 2 m long robotic arm attached to the front of the Perseverance chassis. It has a rotating percussion drill that can be used to collect core samples for return to Earth. The sample return part of the mission is complicated and will be the first samples collected from another planet if all goes well.
Perseverance is equipped with 43 sample tubes. The goal of the mission is to collect at least a dozen samples. The samples are kept in a central location so that they can be retrieved by a future mission.
But perseverance will also perform important analysis itself. The SuperCam instrument, an upgraded version of the Curiosity Rover's ChemCam, will use lasers and four sensitive spectrometers to identify potential chemical biosignatures in rocks and debris. And that from a distance, which makes the rover remarkably flexible. SuperCam can identify the chemical and mineral composition of targets from more than 7 meters (20 feet) away as a pencil tip. Among other things, “soil types” can be identified that are more likely to retain old samples.
This is the mast unit of the SuperCam that is installed on the Perseverance remote sensing mast. It fires a laser at rocks to vaporize them and then uses a spectrometer to analyze their chemical composition. Photo credit: CNES
But all of this scientific research is still a long way off. The spaceship has about four months to go before it lands on February 18. But that's ok; It's not that Jezero crater is going anywhere or changing in any way.
This artist's concept shows a close-up of NASA's Mars 2020 rover examining an outcrop of stratified sedimentary rocks. Photo credit: NASA / JPL-Caltech
Once the rover has reached Mars, it still has to land. Landing on Mars is not easy and is probably the most difficult and dangerous part of the mission.
But if it arrives and can survive its landing, perseverance can go down in history as a mission that uncovered solid evidence of life elsewhere.