Spring time on Earth can be a turbulent affair, as plants return to life and creatures large and small prepare to mate. Nothing like this happens to Mars, of course.
But even in a cold world like Mars, spring weather brings changes, though you have to look a little closer to see them.
Fortunately for us, there are spaceships that circumnavigate Mars with high resolution cameras and we can track the onset of Martian spring time through images.
When winter comes to the polar regions of Mars, a thin layer of ice is deposited on the planet's surface. This is not ice water, but ice with carbon dioxide. Then, when spring comes, as it did in May 2019 in the northern polar region of Mars, the ice of CO2 sublimates, passing directly from solid to evaporation without going through the liquid phase.
In the dunes of Mars, these sublimations occur from the bottom up. This is because the winter ice grains that form the layer become almost transparent, allowing sunlight to melt the ice from the bottom. This traps gas between the ice below and the sand above.
As the warming progresses, the ice cracks, forcibly releasing the gas trapped beneath it.
As it bursts through the ice, it brings dark sand with it. You can see these dark spots in the image below.
 ESA / RosCosmos ExoMars Trace Gas Orbiter arrived in Mars in October 2016, and has been studying the planet ever since.
Part of the payload of his tool is the Color and Stereo Surface Imaging System (CaSSIS), which, among other things, creates detailed digital models of the elevation of Mars.
CaSSIS is a high resolution camera and in May 2019 captured an image of melting CO2 in the northern polar region of Mars.
The image also shows different types of dunes that form on the planet. While the left side of the image looks like dunes, as most people can imagine, the right side does not.
These are called barchan dunes or crescents. These dunes can grow larger and join each other from the barchanoid ridges. The Barchan dunes tell us how the prevailing wind blows: the curved peaks point downwards.
The Trace Gas orbit CaSSIS tool also captures images of springtime in the southern polar region, in May 2018. The image again shows a dune field, but this time inside a crater.
The same type of spring sublimation is present in this sublimation, present with geysers or explosions of buried CO2 ice erupting through surface ice and carrying sand with it. In this dune field, sand is carried over the face of the dunes.
The axial inclination of Mars is about 25 degrees, slightly larger than 23.4 degrees on Earth. The seasons of Mars do not move in lock with the earth seasons. The Martian year is about 687 Earth days, but unlike Earth, the seasons of Mars do not occupy a 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 does not. Its orbit is more elliptical and its velocity varies. So while the terrestrial seasons change on the same date year after year, Mars seasons don't.
Here is an excerpt from a table from the Planetary Authority showing the Martian seasons. There are different ways to measure and mark the seasons of Mars, but this method is used by some scientists.
From left to right: spring equinox, summer solstice, autumn equinox, winter solstice. Click here to see the full thing.
European Planetary Science Congress will meet this week to discuss among other things, the results and images from Trace Gas's orbit.
This article was originally published by Universe Today. Read the original article.