Nothing says that spring on Mars looks like sand explosions

Spring on Earth can be a foolish affair, as plants come to life and creatures large and small prepare to mate. Nothing like that happens on Mars, of course. But even in a cold world like Mars, spring brings changes, even if you have to take a closer look to see them.

Fortunately for us, spacecraft in orbit around Mars are equipped with high resolution cameras and we can follow the beginning of the Martian spring through images.

When winter arrives in the polar regions of Mars, a thin layer of ice is deposited on the surface of the planet. It is not ice water, but carbon dioxide. Then, when spring comes, as in May 2019 in the northern polar region of Mars, CO2 ice sublimates, passing directly from the solid phase to the vapor phase without going through a liquid phase.

In the dune fields of Mars, this sublimation is from the bottom up. This is because the winter ice grains that form the layer become almost transparent, letting the sunlight melt the ice from below. This traps the gases between the ice below and the sand above. As the warming progresses, the ice cracks, violently releasing the gas trapped beneath it. When it explodes through the ice, it carries black sand.

The ESA / RosCosmos ExoMars Organizer Trace Gas Orbiter arrived in March in October 2016 and has been studying the planet since then. The stereo and color surface imaging system is part of the payload of this instrument (Cassis) which, among other things, creates detailed numerical models of elevation of the surface of Mars.

The CaSSIS camera is a high resolution camera. In May 2019, she captured an image of CO2 melting in the North Polar Region of Mars.

The image also shows different types of dunes that are forming on the planet. While the left side of the image looks like dunes as most people imagine, the right side is not. These are called Barchan dunes or crescent dunes. These dunes can grow and meet each other from barchanoid ridges. The dunes of Barchan indicate the direction of the prevailing wind: the curved points point to the wind.

The CaSSIS instrument of the Orbiter Trace Gas also captured images of spring in the southern polar region in May 2018. The picture shows, again, a dune field, but this time inside a crater. The same type of spring sublimation is present in this image, with geysers or explosions of buried CO2 ice crossing the surface ice carrying sand. In this dune field, the sand is dragged on the face of the dunes.

The axial inclination of Mars is about 25 degrees, slightly more than the Earth's 23.4 degrees. The seasons on Mars do not follow the terrestrial seasons. A Martian year is about 687 terrestrial days, but unlike the Earth, the seasons of Mars do not take each quarter of the year. It's because of its orbit.

While Earth's orbit is almost circular and moving at a steady speed around the Sun, Mars is not. Its orbit is more elliptical and its speed varies. So, as Earth's seasons change on the same dates, year after year, the seasons of Mars do not.

Here is an excerpt from a table of the planetary organization showing the Martian seasons. There are different ways to measure and mark the seasons on Mars, but this method is used by some scientists.

The European Congress of Planetary Science will meet this week to discuss, among other things, the results and images of the Trace Gas Orbiter.