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Astronomers have spotted a strange cloud formation lying on Mars in the sky above Arsia Mons, a 12-km-high volcano located near the equator of the Red Planet.
With the help of the Mars Express (MOE) orbiter, researchers from the European Space Agency have been monitoring the cloud since 13 September.
Even though it seems to emanate from the crater of Arsia Mons, the cloud is not related to volcanic activity. It is rather a cloud of water ice driven by the influence of the leeward slope of the volcano, the slope facing the wind, on the surrounding airflow. Known as the orographic cloud or leeward, this feature has already appeared in the region.
In an image taken on October 10 by the MOE's visual surveillance camera (VMC), the white line can be seen extending about 930 miles to the west of Arsia Mons. For comparison, the volcano itself has a diameter of about 270 miles at its base.
It is the second largest volcano known to science in terms of volume, beaten only by its neighbor Olympus Mons. In fact, Arsia Mons has 30 times the volume of Mauna Loa in Hawaii, the largest volcano in the world.
On October 16, the northern hemisphere of the red planet experienced its winter solstice. In the months leading up to the solstice, most cloud activities disappear on large volcanoes such as Arsia Mons. For the rest of the year, its summit is covered with clouds.
However, even before the solstice, it is known that a cloud of water ice such as that shown on the image forms along the southwestern flank of the volcano. It has already been observed by Mars Express and other missions in 2009, 2012 and 2015.
During the Martian day, the cloud spotted by the MOE has a variable appearance, its size increasing to a size so impressive that it can even be seen by telescopes on Earth.
The formation of water ice clouds is sensitive to the amount of dust present in the Martian atmosphere. The latest images – which were captured after a massive dust storm that swamped the entire planet in June and July – will help researchers better understand the effect of dust on cloud development throughout. l & # 39; year.
The big dust storm has posed problems for NASA's Opportunity Rover, which has been operating on the surface of Mars for more than 14 years.
The space agency has had no news of the vehicle since June, after the storm swept the sun, which means that the rover could not recharge its solar batteries. This forced NASA to suspend its scientific activities as the vehicle switched to a state of low energy consumption, which is enough for its critical heaters to work, but nothing more.
NASA has announced that it will pursue the current strategy to try to make contact with Mobile Opportunity in the near future.
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