Remote Sensing and the Mars Perseverance Rover
How imagery from the Mars Reconnaissance Orbiter helped scientists choose the Perseverance landing site
A vital part of NASA’s Mars Perseverance mission was to find a landing spot on the red planet with few travel hazards and a wealth of scientific data. This project uses imagery captured by instruments on the Mars Reconnaissance Orbiter and methods of remote sensing to extrapolate why Jezero Crater was selected as the site versus other possibilities.
NASA used remote sensing technology to decide between thirty potential landing sites for the Mars Perseverance Rover Mission, which is launching in July 2020. After intense scrutiny of the sites, they decided to select Jezero, a 49 km crater in the Syrtis Major quadrangle on Mars, as the landing site.
The Mars Reconnaissance Orbiter (MRO) has been relaying high resolution imagery to scientists on Earth since 2006. Sensors on the MRO record reflected radiation in the visible and infrared portion of the spectrum. With the use of computer programs such as Esri’s ArcGIS, scientists can discern things like the mineral compositions of rocks, the presence of water, and temperature differences based on the spectral response of these materials. Some scientists have used this technology to find clues to potential life on the red planet, such as silicates (Tarnas, 2019) and carbonates (Horgan, 2019). Others have looked at geomorphology of landforms on Mars, such as the delta on the west side of Jezero Crater, in order to study the clay minerals present for their potential to preserve organic compounds (Ehlmann, 2008). All of this work was done mainly with two instruments on the MRO, the Compact Reconnaissance Imaging Spectrometer (CRISM) (Murchie, 2008) and the High Resolution Imaging Science Experiment (HiRISE) (McEwen, 2007). Another instrument, the Context Camera, or CXT, takes images intended to be used as a background for information gathered by the other two instruments (Malin, 2007).
This project compares attributes of three of the final contenders for the Perseverance/Mars 2020 landing site and shows how the data acquired by the remote sensing equipment aboard the MRO helped make the final decision.
The landing site for Perseverance had to fit four main criteria:
•The site had to be geologically diverse, showing signs of the processes that formed it
•The site should be astrobiologically interesting, with signs of possible ancient life
•There should be enough suitable material at the site for collection and caching for possible future pick-up
•The site should contribute new knowledge that will help humans go to Mars
In order to decide between landing sites, scientists used imagery from three cameras on the Mars Reconnaissance Orbiter, which gave them different types of information.
Remote sensing technology has made it possible for us to visit planets in our solar system without ever setting foot on them. The resolution of the instruments on the MRO is so fine that the resulting images can be seen as works of art. But they are so much more than that. The information from CRISM and HiRISE make it possible to discern fine features and to see what minerals are located where. We can see where clays and carbonates and other things that suggest the presence of water are. We can tell which soil is from the surface and what’s been disturbed and brought up from beneath the surface by impacts or volcanism. These instruments remove much of the guesswork from what’s going on at particular sites on Mars. In short, we’ve never had better access to potential landing sites than we do now. NASA was in a position to make a well-founded decision as to where to land the new Perseverance Rover.
An example of an image from CRISM, with bands of reflected light set to be different colors so scientists can see the difference between various minerals. In this case, yellow is olivine, blue is pyroxene. (NASA/JPL/JHUAPL)
An example of an image from HiRISE, where its high-resolution imagery helped discover lava coils on Mars for the first time. (NASA/JPL/UArizona)
The map to the right was made with Esri’s ArcGIS web mapping software. The imagery is a mosaic made using CTX and HiRISE data layers. It shows the final three sites considered for the Mars Perseverance mission.
The top three sites were Northeast Syrtis, circled green on my map, Jezero, circled red, and Midway, circled blue. Midway was actually a last minute addition to the list of sites, and was named Midway for the simple reason that it’s halfway between Jezero and Northeast Syrtis. All three of these sites had a lot of benefits for the mission, and if it hadn’t been for the detail of the information scientists were able to get from remote sensing, the decision might not have been a very clear one. All had characteristics that would fulfill the four objectives discussed earlier.
Northeast Syrtis Site:
•Minerals present at the site suggest possible past habitability
•The site gave potential insight into crustal processes
•But it was hard to define some elements in acceptable detail and time for the mission
Midway Site:
•The rover could visit other sites from this landing
•There is evidence of possible past subsurface life
•But there are also many uncertainties about the origins of the rock here
Jezero Site:
•It has a well-defined fluvial system and clear mineralogy
•There are previously identified points of interest
•There is a diverse watershed/delta
•The rover could also visit Midway from this location
•But features at this site may be very young, making it hard to create a chronology
All three of these sites had a lot of benefits for the mission, and if it hadn’t been for the detail of the information scientists were able to get from remote sensing, the decision might not have been a very clear one. All had characteristics that would fulfill the four objectives discussed earlier. The major thing that detracted from the value of Midway and Northeast Syrtis were some uncertainties of the origins of some of the minerals at those sites, and how well those minerals would preserve organic matter. Jezero Crater was ultimately chosen as the landing site. It has scientific characteristics and points of interest pertinent to the mission objectives, as well as terrain on which it would be safe for the rover to land and operate, increasing the probability of mission success.
It doesn’t take a highly trained scientist to notice that Jezero Crater has a very interesting feature on its west side—a delta from an ancient river that flowed into what scientists believe was a lake that filled the crater. One of the landing site criteria was that the geologic processes that made the site had to be discernible, and while there is some disagreement about the age of these features in Jezero, the fluvial process is well-agreed upon. Deltas on Earth are known to be very rich in nutrients and organics, and so it’s thought the same can be true on Mars. After closer examination, teams of scientists have found clays, carbonates and possible hydrosilicates, all of which are good indicators that signatures of organic matter might be found at the site. Jezero has been deemed safe for the landing and operating of the rover, and there are a wide variety of minerals and rocks here for collection. Not only that, but Jezero is close enough to Midway that a secondary mission could be possible, where the rover can drive out to see what’s at that site as well.
Above is a composite image from CRISM and CTX, with false color applied to the infrared bands to show the mineral diversity of the Jezero site. Clays/phyllosilicates, which can preserve signatures of organic matter, are in green. (NASA/JPL/JHUAPL)
Planning a mission to a planet we’ve never seen in person always has risks involved. But remote sensing makes it possible for scientists and engineers to make these plans with a clearer vision than ever before, and it takes a lot of the guesswork out of the planning phases. When the Mars Perseverance rover lands on Mars in February 2021, we can start learning more about the Martian surface using a different kind of remote sensing—using the instruments on the rover itself.
References:
Ehlmann, B.L., et al. (2008), Clay minerals in delta deposits and organic preservation potential on Mars, Nature Geoscience, Vol 1, 355-358.
Horgan, B.H.N., et al. (2020), The mineral diversity of Jezero crater: Evidence for possible lacustrine carbonates on Mars, Icarus, 339:113526.
Malin, M.C., et al. (2007), Context Camera Investigation on board the Mars Reconnaissance Orbiter, Journal of Geophysical Research, 112, E05S04.
McEwen, A.S., et al. (2007), Mars Reconnaissance Orbiter’s High Resolution Imaging Science Experiment (HiRISE), Journal of Geophysical Research, 112, E05S02.
Murchie, S.L., et al. (2009), Compact Reconnaissance Imaging Spectrometer for Mars investigation and data set from the Mars Reconnaissance Orbiter’s primary science phase, Journal of Geophysical Research, 114, E00D07.
Tarnas, J.D., et al., (2019), Orbital identification of hydrated silica in Jezero crater, Mars, Geophysical Research Letters, 46:22, 12771-12782.
Software Used:
Esri ArcGIS Online Web Mapping
