Mysterious 900 MILE long 'plume' cloud spotted on the surface of Mars near a giant volcano
- Huge cloud is now over 900 miles (1500km) long and began forming near the 20 km-high Arsia Mons volcano
- Scientists believe the vast cloud is not caused by volcanic activity, but is a water ice cloud
- Believed the vast dust storm earlier this year on Mars may be behind its huge size
Scientists are closely tracking a mysterious giant 'plume' cloud on the surface of Mars.
The huge cloud is now over 900 miles (1500km) long, and began forming near the 20 km-high Arsia Mons volcano, close to the planet’s equator.
However, scientists believe the vast cloud is not caused by volcanic activity.
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Since 13 September 2018, the Visual Monitoring Camera (VMC) on board ESA's Mars Express has been observing the of a curious cloud formation. The cloud can be seen in this VMC image taken 10 October as the white, elongated feature extending 1500 km westward of the volcano. The huge cloud is now over 900 miles (1500km) long, and began forming near the 20 km-high Arsia Mons volcano, close to the planet’s equator.
Instead, it is a water ice cloud 'driven by the influence of the volcano’s leeward slope on the air flow' – something that scientists call an orographic or lee cloud – and a regular phenomenon in this region.
'The cloud’s appearance varies throughout the martian day, growing in length during local morning downwind of the volcano, almost parallel to the equator, and reaching such an impressive size that could make it visible even to telescopes on Earth,' the European Space Agency said.
Left, The water ice cloud, which arises as the volcano slope interacts with the air flow, can be seen as the white, elongated feature in the lower left part of the image, extending westward of the volcano and casting a shadow on the surface. The image was taken on 17 September 2018, from an altitude of 11 000 km. North is up. Right, The cloud began forming near the 20 km-high Arsia Mons volcano, close to the planet’s equator. a comparison, the cone-shaped volcano has a diameter of about 250 km; a view of the region with labels is provided here.
ESA’s Mars Express has been observing the evolution of the storm since 13 September.
The formation of water ice clouds is sensitive to the amount of dust present in the atmosphere, ESA said.
These images, obtained after the major dust storm that engulfed the entire planet in June and July, will provide important information on the effect of dust on the cloud development and on its variability throughout the year.
The High Resolution Stereo Camera on board ESA’s Mars Express snapped a view of a curious cloud formation that appears regularly in the vicinity of the Arsia Mons volcano. This water ice cloud, which arises as the volcano slope interacts with the air flow, can be seen as the long white feature extending to the lower right of the volcano. The cloud, which measures 915 km in this view, also casts a shadow on the surface. This image was taken on 21 September 2018 from an altitude of about 6930 km. North is up.
Mars just experienced its northern hemisphere winter solstice on 16 October.
In the months leading up to the solstice, most cloud activity disappears over big volcanoes like Arsia Mons; its summit is covered with clouds throughout the rest of the martian year.
However, a seasonally recurrent water ice cloud, like the one shown in this image, is known to form along the southwest flank of this volcano - it was previously observed by Mars Express and other missions in 2009, 2012 and 2015.
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