Mars Plans Advance (and Occasionally Fade)

Mars has the twin attributes of being close by (at least by solar system standards) and retaining a record of its earliest epoch (lost on Earth) when life might have formed. These have made it a popular destination with five orbiters currently operating around it and two rovers driving across its sands. At least as many new missions are in various stages of development or are proposal, ranging from hardware headed for the launch pad in a few months to some that eventually may prove to be no more than vaporware.

In the last two months, there has been significant news about the European-Russian 2018 mission and about NASA’s 2020 rover. NASA also has announced that it would like to send a new orbiter to the Red Planet in the early 2020s. These announcements will be the meat of this blog post, but first I’ll quickly run through the status of other planned and proposed missions.

Six craft to launch as four missions are firmly in development and have fully funded budgets. Europe’s Trace Gas Orbiter and its Schiaparelli technology demonstration lander are in assembly and on track to launch next January. NASA’s InSight geophysical lander is also in assembly for its launch next March, although the mission’s principal investigator reports that the schedule is tight. Design of the 2018 ExoMars European rover and Russian lander are on track, as is NASA’s 2020 rover.

It’s likely that another mission to return to the Martian northern polar plains has been proposed for the NASA Discovery program. The Phoenix lander explored these regions, but was frustrated by clumpy soils that made it difficult to deliver samples to its instruments. What the Phoenix spacecraft did find was a layer of ice just below the surface dust that could provide a habitat for life. The proposed Icebreaker mission would follow up on the Phoenix mission with a sampling system that would drill well into the ice and is designed to work with the clumpy soil. The lander, which would be a near copy of the Phoenix and InSight landers, would carry new instruments that would search for signs of life. While this proposal has received considerable publicity, I haven’t heard whether it was actually proposed. Sometimes, proposers learn as they develop their plans that their missions would not fit within the tight budgets of Discovery missions. (I’ve heard of one proposal that I was excited about that wasn’t submitted for the current Discovery selection for this reason.) If the Icebreaker mission was proposed and is selected (beating out 27 other proposals), it would launch in 2021.

China announced plans a few months ago for its own Martian rover mission to launch in 2020. More recently, a Chinese official stated that the budget for this mission was unlikely to be approved in time for a 2020 launch.

There have also been press accounts that India is considering a second Mars mission that might be an orbiter and/or a lander. I haven’t heard whether the budget for a follow on mission has been approved or not.

And now on to the major announcements of the last couple of months.

The 2018 ExoMars mission will use a Russian landing system and platform to deliver a European rover to the surface. Russia has planned to use the landing platform as a scientific station after the rover rolls off it. Until recently, I’ve been unable to find any details about the planned experiments. Now an announcement of opportunity has been issued for European scientists to contribute to Russian-led instruments and to propose their own additions (see here). 

The documents state that the priorities for the stations are:

“Priority 1:

• Context imaging;

• Long-term climate monitoring and atmospheric investigations.

Priority 2:

• Studies of subsurface water distribution at the landing site;

• Atmosphere/surface exchange;

• Monitoring of the radiation environment

• Geophysical investigations of Mars’ internal structure.”

The documents lists the names only for an ambitious suite of instruments, although it’s not always clear what instruments are already firmly planned versus those that might be added by European scientists. The instruments break down into several groups:

• Camera
• Meteorology and atmospheric science: Meteorological package, multi-channel Laser Spectrometer, IR Fourier spectrometer, atmospheric dust particle instrument, and a gas chromatograph-mass spectrometer to study composition.
• Ground and shallow below ground: Active neutron spectrometer and dosimeter, radio thermometer for soil temperatures
• Geophysics: Magnetometer and seismometer

This suite would be a highly capable science station. For example, the station will monitor both the physical state of the atmosphere (temperature, pressure, dust load, etc.) as well has changes in its composition (presumably with a focus on changes in trace gases to provide ground truth measurements for the 2016 Trace Gas Orbiter). The listed target weight for the seismometer suggests a simpler instrument than the InSight lander will carry. Having a second seismometer would help geophysicists narrow down the source locations of Mars quakes. The sensitivity of this new seismometer may be limited if there isn’t a way to lower it to the ground to isolate it from the vibrations within the station.

What I am surprised by is that the call for instruments includes requests for significant pieces of hardware to be supplied by European scientists for Russian-led instruments. In terms of instrument and spacecraft development, 2018 is practically around the corner. I will be interested to see how the Russians and Europeans manage the selection, development, testing, and integration of these instruments in this short time frame. Perhaps considerable work has already been done or there are flight-ready designs already available.

Two years after the ExoMars station and rover arrive, NASA will land its 2020 rover. The rover itself will be a near copy of the Curiosity rover currently on Mars, but with a next generation instrument suite. A major new goal will be to select and cache a suite of samples that a later mission might collect and return to Earth. 

Each sample will be about the size of a stubby pencil. Previously, NASA had planned to put each sample into a canister as it was collected. This canister would then be placed on the surface for later collection after it was full. But recently, there has been a major change proposed for how these samples will be cached (see here).

The original plan had two key limitations. First, as the canister acquired more and more samples, it would become an increasingly precious resource. This would lead the mission’s operators to become increasingly conservative in their operation of the rover. Should they, for example, explore an interesting looking ridge, but one where if the rover fails the rock face would prevent a future mission from being able to reach the canister? Second, there was no good way to remove samples once they were in the canister. What if the canister was full and then scientists find the one sample they absolutely want to collect for return to Earth?

In the new plan, dubbed the Adaptable Cache, the rover would still drill out samples and put them into sample tubes. Then instead of putting the tubes into a canister, the rover would place them on the surface and then move on. A future sample return mission would carry a rover that would pick up the samples and place them into a canister it carries. This way the 2020 rover can cache more samples than could be returned and scientists would send the subsequent rover to pick up only the most important ones. Even with the old scheme where the 2020 rover carried the canister, the follow on mission would still need a rover to fetch the canister. Now that follow on rover would need a more capable arm to pick up tubes lying on the surface and place them into its own canister.

The new rover will also have an upgrade to its engineering cameras. On Curiosity, the navcam/hazcam cameras used to operate the rover take black and white images. The 2020 rover will carry color cameras that will take higher resolution images. Curiosity carried just one camera to record its descent and landing, placed on the bottom of the rover to look down. The 2020 rover will carry additional cameras that will look up at the descent stage that carries the descent rockets, a camera on the descent stage looking down at the rover, and a final camera on the backshell to image the parachute opening. 

With these new cameras, being an armchair explorer of Mars will get, as they say, a whole lot better.

In one other item of Mars 2020 rover news, the current cost estimates for the mission appear to be in the $2.14–$2.35 billion range instead of the previously quoted $1.5 billion. A reasonable portion of this increase likely comes from the new figures representing inflation through launch and operations, while the original cost estimates were, I’m told, were in 2015 dollars. At the new figures, the 2020 mission, given inflation, still will be considerably cheaper than the Curiosity mission on which much of the design will be based.

The final major news for Mars exploration was NASA’s announcement that it would like to fly a new orbiter to Mars in the early 2020s (see here). NASA will need a new orbiter to act as a communications relay for future lander missions (such as a sample return fetch mission). The agency could fly a fairly simple orbiter to do just this task. Instead the agency is considering flying a highly capable orbiter that would use solar electric propulsion (SEP).

All previous Mars missions have used rockets to enter Mars orbit. Solar electric engines, such as those used by the Dawn and Hayabusa2 missions, provide a great deal more cumulative thrust. By using SEP, the new orbiter could spiral into Martian orbit. At it lowers its orbit, it could rendezvous with each of Mars’ tiny moons for in-depth studies. Then the orbiter could switch from a near equatorial orbit (where the moons are) to a polar orbit to allow it to study the entire Martian surface. 

NASA’s Mars program manager stated that the agency would like to have the orbiter carry a substantial scientific payload (one chart lists a capability to host up to 300 kg of instruments, which would be a very substantial payload). The agency has not stated a preference for what types of instruments – a future scientific definition team would make those recommendations. However, we can do some informed speculation.

In the 2000s, two scientific definition teams looked at science that then future orbiters could make. The highest priority measurements would be to study the upper atmosphere and trace gases in the atmosphere. Time has moved on, and the MAVEN orbiter is at Mars studying the upper atmosphere and the 2016 European-Russian orbiter will study trace gases.

The panels in the 2000s did recommend that future orbiters carry high resolution cameras to image possible landing sites and carry out scientific imaging. Since the mid-2000s, the HiRISE camera on the Mars Reconnaissance orbiter has been imaging the planet at 25 to 32 cm pixel resolution. The HiRISE team described a possible future instrument that would use the same optics, but would provide color imaging across the entire image. (See here.) (The current HiRISE camera has color only for the center fifth of each image.) A future camera also could add imaging in spectral bands in the near infrared that would allow studies of surface composition at high resolution. This future camera could also acquire stereo images to allow 3D analysis of each scene.

Another concept for a future high resolution camera comes from Malin Space Science Systems, who has built cameras for several Mars missions. (See here.) This camera would carry a bigger telescope than HiRISE camera, and the orbiter would fly closer to the planet—skimming just above the top of the atmosphere at perihelion—to acquire images at 5 to 10 cm pixel resolution. This finer resolution would allow more detailed scientific studies of surface features, such as the fine sedimentary bands that are often almost visible in current HiRISE images. (The published abstract for this proposal doesn’t discuss whether the camera would image in multiple color bands. It also doesn’t say how narrow the image strips would be. HiRISE’s lower resolution likely would provide wider image strips.)

Another proposal suggested that a future mission might carry a suite of radar instruments and laser to map the surface and subsurface in detail. (See here.) Ground penetrating radar instruments are already at Mars mapping the subsurface stratigraphy. However, their capabilities are limited by the power and mass available to them within the overall suite of instruments the orbiters carried. The proposal suggests that a future orbiter carry one radar optimized for subsurface stratigraphy and a second for surface mapping that would be able to penetrate the sand and dust that covers much of the planet to image the rock structures below. The proposal also recommended flying a new generation Laser Ranging and Detection (LiDAR) instrument that would remap the altimetry of the surface at much higher resolution. A new orbiter such as the one NASA is discussing would have the power and payload mass to optimize instruments such as these along with a high resolution camera.

Another key capability of the proposed orbiter is that it would use laser optical communication to return data to Earth as well as newer generation radio systems (Ka band). The limit on how much data past and current orbiters have been able to return has not been the instruments, but instead the bottleneck of the communications system. High resolution cameras and radar instruments want to be data hogs, and a new generation orbiter with advanced communication could be an enabling technology to map much larger areas of the planet at high resolution.

This orbiter has just been discussed publicly as a concept for the first time in the last couple of months. None of NASA’s scientific panels have looked into missions past 2020. They may recommend another mission instead. It’s also not clear where the money for the mission would come from. NASA’s planetary program will be funding the development of the $2 billion-ish Europa mission in the early 2020s. If the agency also wants to continue developing a mixture of the smaller Discovery and New Frontiers missions in the same time frame, a major new Mars orbiter may stretch the budget. A next generation Mars orbiter would provide new instrument eyes to study the fourth planet. We will need to wait and see whether the programmatic priorities and budgets line up to enable it to fly.