Tuesday, 20 October 2015

The Green, Green, QGIS of Mars

There are many blog posts on the Internet and even scientific papers on the evils of the spectral/rainbow colour palette for continuously varying data.

The series of 6 by Robert Simmon on NASA's Earth Observatory website is particularly worth reading and references many interesting and potentially useful sources.

Incidentally while looking for that, I saw this Image of the Day of a landslide onto a glacier in the Yukon in Canada. I wonder how often they have landslides on Mars.

Thus, I now show you the north of Mars, with the elevation encoded in a single hue palette and again overlaid with "Hard Light" on the Mars Global Surveyor image mosaic.

This will not be perfect for a quantitative visualisation, since it is not possible to distinguish between intrinsically darker areas and areas that are low in elevation.

I choose the green colour, because it leaves red and blue free to plot the classifier function values for areas similar to glacier head and extents.

The various individual HRSC tiles also have the same kind of colour palette of DTM elevation scaled locally overlaid on the nadir image HRSC. Download a larger image of this here.


  1. The detailed mosaic image is awesome. Thanks for the link on colours too.

    Did you draw any conclusions from looking at possible traces of Martian glaciers on likelihood of 'dry' landslides there at this time? (And are there any measurements yet of seismic activity on Mars?)

  2. Landslides do happen on Mars: one set off perhaps by a meteorite impact, HiRISE image of four actually caught in motion.

    I haven't drawn any conclusions about landslides from this data but I expect if you have some mix of debris and ice, and the ice is able to sublimate away over time, the debris could become poorly consolidated and suffer slope failure.

    The NASA InSight lander is expected to include a seismometer http://insight.jpl.nasa.gov/technology.cfm, and also will include a "mole" similar to the one Beagle 2 carried.