Delving under the surface of Mars

The InSight mission will be a trove of information about the red planet’s interior.

Planned for 2018, the InSight mission will place instruments on the surface of Mars to send information back to Earth about the planet’s interior. Mark Panning, a seismologist working on the mission, tells us what he and his colleagues expect to learn, and what they’re doing now to prepare. For updates on his research, follow the project on ResearchGate.

ResearchGate: What is the InSight mission to Mars? 

Mark Panning: InSight is the first mission to Mars focused on learning about the interior of the planet rather than surface or orbital observations. We have three main experiments:

SEIS (Seismic Experiment for Interior Structure) involves placing a package containing two seismometers on a leveling tripod on the surface of Mars via a robot arm. These will be covered up with a wind and thermal shield to reduce the instrument noise. We also have a suite of meteorological instruments and a magnetometer, which will allow us to correct for other sources of noise, but will also likely give us a lot of interesting science results in its own right.

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Artist concept of InSight lander on Mars. NASA/JPL-Caltech

HP3 (Heat flow and Physical Properties Package) is a probe that will dig down up to five meters into the ground and make detailed temperature measurements that will tell us how much heat is coming from the interior of Mars.

And finally, RISE (Rotation and Interior Structure Experiment) will use very precise tracking from onboard radio communication devices to look for small variations in planetary rotation. That can give us information about the deep, internal structure of Mars, just as we can make inferences on how much milk is in a jug by shaking it around.

I’m a seismologist, so my work is primarily associated with SEIS, whose instrument Principal Investigator is Philippe Lognonné. Basically, the combined goal of all the experiments is to understand the interior structure and evolution of Mars.

RG: What is currently known about the seismology of Mars?

Panning: There has been one functional seismometer on Mars, but it was on top of one of the Viking landers, and was not a particularly sensitive instrument by modern standards. There may have been one marsquake recorded on it, but that is debatable. Regardless, most of what it measured was the impact of wind blowing on the lander. This lack of observation tells us Mars is much less seismologically active than the Earth.

That’s not surprising, since there’s no convincing evidence of plate tectonics on the surface of Mars, but Mars isn’t entirely dead geologically speaking. It has several large volcanoes and is still losing heat, meaning it is thermally contracting, which should cause quakes. We can bracket Mars somewhere between the relatively low rate of seismicity measured on the moon—where several of the Apollo landing missions placed seismometers—and the much higher rate of seismicity on the Earth.

On top of this, researchers have made observations of freshly appearing boulder trails in several canyons. These are thought to be widespread rock falls from recent significant marsquakes, so there’s very good evidence that there will be seismicity to observe.

RG: What new information can the InSight mission tell us?

Panning: InSight will nail down a lot of details on the internal structure of Mars. For example, not much is known right now about the density and size of Mars’s core. The RISE experiment should decrease this uncertainty by a factor of 10 or so. This will help answer questions like why Mars had no magnetic field for most of its history, yet continues to be volcanically active. We will also get a good idea of the thickness of Mars’s crust at the landing site and the current tectonic activity level on Mars, which is impossible to do from orbital observations.

NASA's InSight Mars lander spacecraft in a Lockheed Martin clean room near Denver. As part of a series of deployment tests, the spacecraft was commanded to deploy its solar arrays in the clean room to test and verify the exact process that it will use on the surface of Mars.
NASA's InSight Mars lander spacecraft in a Lockheed Martin clean room near Denver. NASA/JPL-Caltech/Lockheed Martin

RG: What research have you done so far to prepare for the mission? 

Panning: To prepare I have been testing how we can deal with the seismic data from the mission. One of the biggest challenges we had when we proposed this mission was the perception that it was very difficult to obtain useful results using only a single seismic station. Most of the seismic work on Earth uses networks of seismometers distributed around the world. Earthquake location methods typically rely on at least three instruments, and so most people have the impression that it is not possible to locate events with only one station. My work in the proposal phase and in the early phases focused on demonstrating the clever techniques we can use to locate events with a single station. One method relies on surface waves that travel all the way around the planet. This should work even better on Mars, as its radius is half that of Earth.

RG: And now? 

Panning: In the near-term, I am co-lead for the Mars Structure Service with Philippe Lognonné. Until we get data back from Mars, we are developing and verifying the techniques and software necessary to recover interior structure models from the data. We’ve got researchers from all over Europe, North America, and Japan contributing to this effort.

The ongoing work to make sure everything is ready to go as soon as the data starts arriving is important. That way, when the data comes, we’ll be ready to make discoveries and get them out to the community as soon as possible. Our mission will be making our data available to all active researchers around the world. This is wonderful for getting the best results from this mission, but it creates some additional pressure to rapidly produce results for the community.

RG: Could there be any surprises in the data that comes back from Mars?

Panning: It’s exciting to be involved in a mission of a truly exploratory nature. Because we haven’t recovered seismic from internal events on Mars before, we can be absolutely certain that the data we get back will be very surprising in some fashion or another. When the first Apollo seismic data from the Moon arrived, the seismograms did not look at all like Earth records. Seismic energy on the moon was extremely scattered, unlike any environment on Earth, due to the very dry and fractured material near the surface of the moon. Undoubtedly, Mars will find some other way to surprise us.

Featured image courtesy of ESA/DLR/FU Berlin.