The Mars Reconnaissance Orbiter exploration probe spotted frost on Mars, covering the sand dunes at the bottom of one of the craters. In some places, the frost melted for some unknown reason, covering the dunes with small dark specks
Snapshot under degree
The photograph, published by the HiRISE team, shows a small patch of the Martian surface at the bottom of an unnamed 20-kilometer-long crater located east of the giant Proctor crater at a latitude of about 47 degrees south of the equator. Its entire bottom (as well as the bottom of Proctor) is covered with sand dunes, which are widespread in this region of Mars.
The photo was taken three years ago, on November 25, 2006, from a distance of 250 km. The original image shows details about a meter in size. Scientists deliberately took this image in the late afternoon, when the Sun was only 10 degrees above the horizon. Thus, oblique rays illuminated sandy waves of various sizes in extreme relief - from huge dune shafts several kilometers long, similar to folds of chocolate silk, to small ripples in meters wide, which resemble fingerprints of a giant palm.
Where does the wind blow from
Precipitation
Hoarfrost is a
thin layer of ice crystals formed on the surface from water (on Earth) vapor contained in the atmosphere. The maximum possible concentration of vapor in the air decreases with temperature, therefore, when it comes into contact with cold objects, part of the vapor turns into ice crystals, which settle on the surface. In summer, instead of ice floes, small droplets of water settle; it is dew.
But, of course, the main focus in this photo is the vast areas of white. According to scientists, this frost is the thinnest layer of crystals of water or carbon dioxide ice on sand and dust. It appears in the same way as the earth's frost: the temperature of the Martian surface at night is slightly lower than the air temperature, and upon contact with it, small amounts of water or carbon dioxide crystallize. During the day, white frost also heats up worse than the dark dust surrounding it, so every next night the white areas grow a little - both in thickness and in breadth.
The photo shows that snow is concentrated mainly towards the eastern (right) slopes of the dunes. During the day, they are in the shade longer, and therefore, on average, it is colder, the specialists of the HiRISE team believe. From here it is easy to understand which dune slopes are flatter and which are steeper, and determine where the wind is blowing from. In the area of Proctor Crater, westerly winds prevail, as in most places on Earth. This is not surprising - Mars is spinning in the same direction as our planet. In addition, there are no oceans on Mars these days that could significantly distort the overall picture.
Promotional video:
Darker than dark
There are other interesting details in this picture. On the finely rippled eastern slopes of the dunes, small dark specks are visible, as if a photograph had been sprinkled with small drops of water. However, there is no water in the HiRISE instrument, and this photograph is exclusively electronic.
Scientists are cautiously suggesting that the frost in these spots evaporates faster than in the surrounding areas. Why is difficult to say. If you look closely, you can see that the dark spots are located in the centers of the frosty areas of the surface, but darker than the surrounding non-frost dust. What this tone means, scientists do not yet know.