My favorite part is when people have questions for us – even when I don’t know the answers. Because, honestly, that’s what science is – we don’t always have the answers, but that’s what makes it exciting! It’s also fun to find out which aspects of the mission inspire other people, and I get a different perspective on what they think is interesting (versus just what I think is interesting!). Some of the questions are really good, too! We were talking with some middle-school students from El Paso, Texas, and their questions were so astute. One girl asked, “Does Mars have plate tectonics?” Another good question was, “How do we know about the interior of Mars?” These are great questions, and HiRISE is helping scientists to answer these and other questions, along with data from many other instruments studying Mars.
In case you were curious about these particular questions, like these kids were, here are some short answers and references for more information:
- Does Mars have plate tectonics?
It doesn’t now, but it might have in the past. The crust of Mars is thicker and stronger than that of Earth, so it’s more difficult to break it apart into plates and start subducting them below one another. However, there is some evidence that Mars may have had active plate tectonics early in its history. Maybe the presence of water in the crust weakened the rock enough to allow plate tectonics. HiRISE is investigating evidence of water in the Martian past, which may help illuminate this issue.
For more reading:
- “Plate Tectonics . . . on Mars” Science News Magazine Volume 155, Number 18 (May 1, 1999) (article)
- Sleep, N.H. 1994. Martian plate tectonics. Journal of Geophysical Research 99, 5639. (scientific paper)
- Nimmo, F., Stevenson, D.J. 2000. Influence of early plate tectonics on the thermal evolution and magnetic field of Mars. Journal of Geophysical Research 105, 11969-11980. (scientific paper)
- How do we know about the interior of Mars?
HiRISE and other cameras can only take pictures of the surface of Mars. So how do we know so much about what’s inside the planet? For example, we know that Mars has an upper crust, a mantle, and a dense core, like the Earth.
One way to see beneath the surface is to use impact craters – they punch holes through the crust and expose deeper rocks. HiRISE has imaged a lot of craters! There is also an instrument on the MRO spacecraft with HiRISE called SHARAD, which uses radar to see buried layers of rock and ice. We know about the deeper interior of the planet from spacecraft that have been orbiting Mars for decades and measuring how gravity, heat flow, and the magnetic field vary over different areas. We can also measure the elevation of different features, and that tells us something about what’s underneath. For example, a tall mountain may have very deep roots that extend into the mantle. Scientists also make theoretical models of the planet based on what we know about the physics and chemistry of how it formed and has evolved. There is still a lot of work to be done in this area, and scientists hope future missions will tell us more about the Martian interior. For example, a seismic
For more reading:
- “Martian Interior” (2007) European Space Agency. (article)
- Zuber, M.T. 2001. The crust and mantle of Mars. Nature 412, 220-227. (scientific paper)
- Planetary Interiors by W. Hubbard (book, general to all planets)