Unlike the constellation of meteorological satellites that surround planet Earth to capture every storm and provide data for future forecasts, no spacecraft fly around Mars solely to measure weather conditions on the Red Planet. Just one of the six spacecraft in orbit around Mars, the Mars Reconnaissance Orbiter, contains a color imager to track daily and seasonal variations in the Martian climate.
But static, daily images cannot adequately capture the dynamic and often ephemeral nature of Martian weather systems. And some of this weather is remarkably Earth-like, with cold fronts, cumulus clouds, and linear features known on Earth as cloud streets among the features that occur in the thin Martian atmosphere.
So geologist and amateur astronomer Justin Cowart decided to see if he could fiddle with images captured by the High Resolution Stereo Colour Imager (HRSC) instrument onboard the European Space Agency’s Mars Express orbiter, which produces stereographic color maps of Mars. In a blog post at The Planetary Society, Cowart explained how he transformed this data into short movies of Martian weather:
To do this, HRSC uses a set of 9 pushbroom sensors. Four of these sensors image the surface in color at blue, green, red, and near-IR wavelengths. The other five collect stereo and photometric data using broadband filters that cover… roughly the same spectral range. The sensors are mounted at different angles, looking between 20 degrees ahead and behind the spacecraft. Parallax from the five different viewing angles allows mission scientists to create DEMs of the surface with 10 to 15 meter vertical resolution.
That’s the intended purpose, anyway. The offset viewing angles for the sensors onboard the spacecraft allow for something else: time-lapse images. The imaging setup means that the first imaging channel sees the surface about 70 seconds before the last. If the wind is blowing at the surface, the time between sequential images is just long enough that the motion of dust clouds is visible. If clouds are at higher altitude, then the parallax also shows up as motion. The color data can then be overlain to colorize the scene.
Cowart says he only tapped into a small amount of the more than 10,000 images collected by the HRSC, which has observed Mars since 2005. For other amateur astronomers, then, more Martian weather likely awaits.
Listing image by ESA / DLR / FU Berlin (G. Neukum) / Justin Cowart