Well, this week has been tied up with attending the NASA Mars 2020 rover site down selection workshop. I was able to spend 2.5 days there and can pass on some of the discussion, but first we should cover some of the upcoming astronomy events.
In November, it is time again for the Nightfall event in Borrego Springs. This is a great opportunity, sponsored by the Riverside Astronomical Society, to meet up with many other amateur astronomers and enjoy the dark skies of the desert. I understand that the closest hotel rooms are all sold out, but hope to see you all there.
Again, later in November we have the AAVSO annual meeting this time held in Flagstaff, AZ. This should be a great opportunity to learn from the most avid variable star observers and have a tour of Lowell Observatory too, all the while enjoying the cool forest environment. Hope to see you there!
Now, back to the NASA Mars 2020 workshop held at the Hilton Hotel in Glendale, CA, on October 16-18, 2018. This 4th and final workshop is held to down select from four potential landing sites to just one actual landing site. The rover for this mission will carry advanced instruments and be powered by radioisotope electric generators and won't be hampered by solar cell dust. One of the new instruments is a ground penetrating radar system which can look up to 30 feet below the Martian surface. This will be the first time a ground penetrating radar has been used on another planet. The Chinese moon rover was the first to use ground penetrating radar on the moon.
The goals of the Mars 2020 mission are summarized in this slide below. One of the key goals is not just to do science from the rover, but to collect samples, now just limited to 20, and cache them for eventual return to Earth, by a future space mission, for more detailed analysis.
|Mars 2020 Rover goals and objectives (Source: NASA)|
Ok, so its off to Glendale I go, where I met up with Math Whiz, Dave, where we both settled in to review and hear about the four proposed landing sites. I got some chocolate chip cookies from the hotel store to share because we are both kind of chocolate cookie monsters.
|Resident Astronomer, AKA Citizen Scientist, and cookies at Mars 2020 Workshop (Source: Palmia Observatory)|
There was something like 200+ scientists from various universities and NASA and JPL offices in attendance. I was there wearing my Citizen Scientist badge. This was a great opportunity to see science being made. In this venue, each speaker had either 10 minutes or 15 minutes to speak and then after 4-5 speakers, there was a general period of time for questions and discussions. With all the experts in the room there was a lot of back and forth and questioning of assumptions and admonitions to consider more data. Also, as it turns out, the session coordinators were very punctual tin starting and stopping speakers, so after I had photographed some interesting slide, all I had to do to check who the speaker was, was to check the time of the photograph with the time listed in the workshop schedule.
|200+ Mars scientists gather at Mars 2020 Workshop to argue for the site that has most scientific merit|
Now, my astronomical interest lies more in the areas of cosmology and astrophysics, so I knew I had better come prepared with a planetary sciences textbook, so that I could look up the big words and concepts the real scientists would be using in their presentations and discussions. So, this book by Pater and Lissauer is one of the best that I have seen. It is mostly self contained and it covers the whole range of sub-topics such as solar system dynamics and heating; planetary surfaces, interiors and atmospheres; magnetic fields; comets, asteroids, and meteorites; planetary rings and planet formation and even exoplanets. I especially like the problems at the end of each chapter. Just in these 2.5 days that I have been reading the book, I found the problems, quite difficult on first read through and then when it dawned on me what I had just read, the approach to maybe eventually solving the problem became apparent.
|During the scientific presentations, this citizen scientist looked up the terms used (Source: "Planetary Sciences")|
In addition to this textbook, I had previously obtained some rock samples of olivine and serpentine. See below. These Earth samples are important in Mars geology because to make serpentine you start with olivine and then through geologic processes with water, you can make serpentine. So, if you find serpentine on Mars, you know that water at one time was present.
|Samples from Earth of Olivine and Serpentine (Source: MiniMe Geology for Palmia Observatory)|
Just in case you want to take a look at the chemistry behind serpentinization, the basic reactions where water and carbon dioxide react is shown below. These minerals, when they are found on Mars, indicates that in the geologic past, there was plenty of water available to enable the chemical reactions that convert one mineral into another one. Also tracking the key locations where carbonates are found is another key geological indicator of previous surface water. The detection of these minerals on Mars is done by onsite rovers now and also by spectroscopic scanning by orbiting spacecraft. Two instruments, which came up in discussion were the ESA OMEGA imaging spectrometer and the NASA CRISM (Compact Reconnaissance Imaging Spectrometer for Mars) on orbiters. The imaged spectra can be analyzed and the mineral on the surface can be identified. The use of these spacecraft instruments is crucial to identifying possible landing sites in order to further the search for when and where water was present on the Martian surface. Also where there was water in the past, there might be signatures of biology or life.
|Finding serpentine and magnesite minerals is an indicator of water at one time on Mars (Source: L. Hallis+/NASA Mars2020 Workshop)|
Determining when and where liquid water was on the Martian surface is a key part of the rover's mission. Evidence of water will be left in the minerals formed and found. It is also in these locations where biosignatures of life might be found.
|Ancient climate, either wet or dry, will leave behind geological evidence (Source: K. Lynch+/NASA Mars 2020 Workshop)|
There was a lot of discussion about picking the right location for the next rovers. One of the key factors is to ensure that the landing site is old enough to contain evidence of the time when water was present on the surface of Mars. One of the key methods for establishing estimates of the age of Martian landscapes is to count the number of impact craters. This technique has been used very successfully on the Moon and is being applied to Mars too. There was some discussion about the uncertainties still outstanding in the use of crater analysis. It seems that only by "ground truthing", examining real samples on the surface, will the age uncertainty be reduced. For right now, picking the right age of deposits is key to selecting the rover landing site.
|Using studies of craters on Moon and Mars to estimate age of geologic formations (Source: B. Bultel+/NASA Mars 2020 Workshop)|
Man of the presentations described the science that was to be possible at each of the potential landing sites as well as the hazards that might cause the rover to get stuck and end its useful mission. The following slide shows one instance of locations that the geologists wanted to sample the Martian terrain and the potential location of hazards. The proposed traverse is shown as the white line in the following slide. There is a tradeoff between where the scientists want to take a sample and the engineers that must find a path between the landing site and all of the remaining sample locations.
|An example of rover traverse planning to avoid hazards and collect samples (Source: NASA Mars 2020 Workshop)|
Another constraint that goes into selecting the next landing site is how close together the really neat geologic formations are and how easy is it to get the rover to those sites. We heard that the design life of the 2020 rover is 1.5 Martian years. Now many NASA rovers and satellites perform much longer than their design life, this lifetime is what is planned for and if the rovers last longer than that, then the possibility of doing extended missions is also being investigated and planned for.
It is also interesting to recall that the rovers move at what we think of on Earth as pretty slow ground speed. This newest rover is expected to move at speeds between 60-130 meters per Martian day. Pretty slow! But, that is in addition to avoiding hazards, it includes the time to stop and take measurements.
Remember too that even though the Martian day is just a little bit longer than an Earth day, just 24 hours and 39 minutes. But because Mars orbit is further away from the Sun, the planet moves around the sun at a slower rate and it takes 687 Earth days for Mars to make one orbit around the Sun.
The last half day of the workshop was when the participants summarized their positions regarding which of the four locations would offer the best scientific perspective on the climate history and biosignature possibilities on Mars. We could see that scientists studying Mars are also very human and made some in additional to strict logical arguments, some passionate responses, also. At the end of the next several days, the final decision rests with NASA Associate Administrator Thomas Zurbuchen, who addressed the audience and said he was there to listen and then hopefully make the best decision for the advancement of the science of Mars for both NASA and its European partners, and for the world. For me, all of the sites were new and I spent most of my time trying to understand all of the geological lingo, but for some reason formed my impression that some site like Midway or NE Syrtis would be the most productive site. Time will tell!
So that is my brief summary of the Mars 2020 workshop, but there are many other resources on the web for more of the details. But if you want to do your own observing of Mars, now is a great time to go outside and check it out. Mars is just a few degrees to the right of the moon right now.
Until next time,
Resident Astronomer George
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