Mars Express keeps an eye on curious cloud

October 26, 2018, European Space Agency
Elongated cloud on Mars. Credit: ESA/GCP/UPV/EHU Bilbao, CC BY-SA 3.0 IGO

Since 13 September, ESA's Mars Express has been observing the evolution of an elongated cloud formation hovering in the vicinity of the 20 km-high Arsia Mons volcano, close to the planet's equator.

In spite of its location, this atmospheric feature is not linked to volcanic activity but is rather 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 can be seen in this view taken on 10 October by the Visual Monitoring Camera (VMC) on Mars Express – which has imaged it hundreds of times over the past few weeks – as the white, elongated feature extending 1500 km westward of Arsia Mons. As a comparison, the cone-shaped volcano has a diameter of about 250 km; a view of the region with labels is provided here.

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 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.

Mars elongated cloud – 21 September. Credit: ESA/DLR/FU Berlin, CC BY-SA 3.0 IGO

The cloud's appearance varies throughout the martian day, growing in length during local morning downwind of the , almost parallel to the equator, and reaching such an impressive size that could make it visible even to telescopes on Earth.

The formation of water ice clouds is sensitive to the amount of dust present in the atmosphere. 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 elongated cloud hovering near Arsia Mons this year was also observed with the visible and near-infrared mapping spectrometer, OMEGA, and the High Resolution Stereo Camera (HRSC) on Mars Express, providing scientists with a variety of different data to study this phenomenon.

Mars elongated cloud – 17 September. Credit: ESA/CNES/CNRS/IAS

Explore further: Mars upside down

Related Stories

Mars upside down

December 14, 2017

Which way is up in space? Planets are usually shown with the north pole at the top and the south pole at the bottom. In this remarkable image taken by ESA's Mars Express, the Red Planet is seen with north at the bottom, and ...

Image: Mars dust storm

July 20, 2018

The high resolution stereo camera on board ESA's Mars Express captured this impressive upwelling front of dust clouds – visible in the right half of the frame – near the north polar ice cap of Mars in April this year.

Lava tubes on Pavonis Mons

May 23, 2006

These images, taken by the High Resolution Stereo Camera (HRSC) on board ESA's Mars Express, show Pavonis Mons, the central volcano of the three 'shield' volcanoes that comprise Tharsis Montes.

Mystery solved regarding largest volcano in the solar system

May 9, 2016

Scientists from the Division of Planetary Sciences and Remote Sensing in the Institute of Geological Sciences at Freie Universität Berlin have succeeded in creating a model simulating the formation of mysterious structures ...

Webcam on Mars Express surveys high-altitude clouds

October 17, 2017

An unprecedented catalogue of more than 21 000 images taken by a webcam on ESA's Mars Express is proving its worth as a science instrument, providing a global survey of unusual high-altitude cloud features on the Red Planet.

Recommended for you

New eclipsing cataclysmic variable discovered

January 21, 2019

Using the Mobile Astronomical System of Telescope-Robots (MASTER), an international team of astronomers has detected a new eclipsing cataclysmic variable. The newfound object, designated MASTER OT J061451.70–272535.5, is ...

Total lunar eclipse woos sky watchers

January 21, 2019

An unusual set of celestial circumstances came together over Sunday night and the wee hours of Monday for sky watchers in Europe, Africa and the Americas, where the moon was fully obscured before lighting up again with a ...

Making stars when the universe was half its age

January 18, 2019

The universe is about 13.8 billion years old, and its stars are arguably its most momentous handiwork. Astronomers studying the intricacies of star formation across cosmic time are trying to understand whether stars and the ...

3 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

Nik_2213
5 / 5 (1) Oct 26, 2018
Must wonder if some exceptional 'cloud roads' contributed to the early, 'false positive' sightings of those purported 'Martian Canals' !!
rrwillsj
not rated yet Oct 27, 2018
Of course the Martian cloud is curious! If some uninvited strangers were poking around, diggimg holes in your backyard? Wouldn't you "express" some "curiosity"?
TheGhostofOtto1923
not rated yet Oct 27, 2018
Methane volcano

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.