This is a question at the nexus of image interpretation and methodology of planetary science.

  • How can HiRISE images be used in confirming or refuting hypotheses about the past and present geology of Mars in the areas which our rovers haven't explored?

  • Have there been any meta-studies on the diversity of sources used in scientific articles (e.g. HiRISE alone, HiRISE + THEMIS, HiRISE with digital terrain models etc.) on Martian geology? How many scientists down here rely on their interpretation of imagery?

  • How many of the ideas proposed in the articles were subsequently disproven by in-place exploration by the rovers?

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    $\begingroup$ I think this should possibly be broken up into two different questions, since questions 1 and 2a are very different. Question 2b is yet another question concerning the relationship between orbital observations and surface observations, so really there are three different topics here... $\endgroup$ Aug 7, 2013 at 9:15
  • $\begingroup$ @robguinness - thanks for the idea, I'll try to save the question - the underlying (and unifying) topic is that of reasoning about processes on Mars using satellite imagery instead of boots on the ground. $\endgroup$ Aug 7, 2013 at 9:19
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    $\begingroup$ And that's an interesting topic. My point is that when I read "How reliable is HiRISE imagery..." I start to think about HiRISE in particular and what have we learned from about Mars from that specific instrument. But the larger question of learning about Mars from Mars orbit would be phrased differently and probably attract a different audience as well. $\endgroup$ Aug 7, 2013 at 11:39

1 Answer 1


Each instrument on Mars, or any other planet, has strengths and weaknesses. Used together, you get a whole picture.

HiRISE can take visible and near visible images, in very high resolution. There's a lot that can be learned from this that is harder to learn with poorer resolution. Visible images will allow you to see real objects, and in particular, how they change with time. It is easier to relate to these images than those with other images. Furthermore, it is extremely useful in seeing exactly what is on the surface for making landing attempts, for instance.

THEMIS, for instance, is infrared. One of Infrared's strengths is to determine the size of surface particles. It can tell the difference between sand, bedrock, and boulder fields, for instance. One of the things that HiRISE has done to address THEMIS data is to confirm some of the sand/boulder fields that THEMIS has seen.

In this case, it isn't that one or the other isn't reliable, it's just that the show very different things. In fact, it is extremely common to use multiple sources to publish papers. The knowledge of the digital elevation map is actually used in the planning process for all images, and at least when I worked at HiRISE, THEMIS images were used to help plan where to shoot HiRISE, as they were the highest global resolution images of the planet. Perusing the internet, I see many references to using THEMIS and HiRISE data together, such as Possible Chloride Salt Deposits Observed in THEMIS, EXTENDING CRISM SPECTRAL COVERAGE IN GALE CRATER USING THEMIS VIS AND HIRISE., and IDENTIFICATION AND ANALYSIS OF ROOTLESS VOLCANIC CONES ON MARS.


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