The images in the Martian Cloud Atlas have been captured by the High Resolution Stereo Camera (HRSC) instrument on ESA’s Mars Express spacecraft.
Lee waves on Mars are created by the wind encountering obstacles and build up on the ‘leeward’ or downwind side. Image credit: ESA / DLR / FU Berlin.
Due to the elliptical orbit of Mars Express, its HRSC camera can not only take surface observations from low altitude to map the planet at the highest possible resolution, but also capture observations from higher altitudes at lower resolution, covering much larger parts of the surface with a typical field of view from limb to limb.
These high-altitude observations are ideal for observing atmospheric phenomena on Mars.
After more than 20 years of the Mars Express mission, an extensive amount of image data on atmospheric phenomena on Mars has been accumulated, which has a great potential for scientific exploitation.
“Clouds on Mars are just as diverse and fascinating as those we see in our skies on Earth, with some features unique to the Red Planet,” said Dr. Daniela Tirsch, a researcher at the German Aerospace Centre (DLR).
“One of my favorite phenomena are the beautiful ‘cloud streets’ — linear rows of fleecy clouds that develop around the huge volcanic Tharsis rise and the northern lowlands in northern spring and summer.”
“While they resemble cumulus clouds on Earth, they are formed under different atmospheric conditions.”
“We also see impressive dust clouds that can spread hundreds of km — a phenomenon we luckily don’t experience on Earth.”
Dust plays a major role in the atmosphere and climate of Mars.
Rare upwelling events can leave beige, dust-laden blobs hanging in the planet’s atmosphere.
Large differences in temperature and air pressure at certain seasons can result in stronger-than-usual winds that lift large amounts of dust from the Martian surface.
Dust clouds spreading from the tops of giant volcanoes take on the appearance of eruption clouds, although they are no longer active.
Large spiral dust storms and cyclone systems can also be observed each year near the Martian north pole.
Studying these phenomena is crucial to scientists in understanding the atmosphere and air mass circulation on Mars.
Rippling ‘gravity clouds’ are one of the most common formations on both Mars and the Earth.
They are seen at mid-latitudes in winter for both hemispheres, as well as over the Tharsis volcanic plateau in southern winter.
Lee waves, a special type of gravity clouds, can build up on the downwind side of ridges, mountains and other obstacles to create repeating ridge formations.
Some types of clouds studied are specific to locations and seasons; others like ‘twilight clouds’ can appear in the early morning at any place or time of year.
The new atlas will provide valuable insights into the physical nature and appearance of clouds and storms, the time of their occurrence and their location.
This knowledge will help better understand the atmospheric dynamics and the climate cycles on Mars, as well as providing input for studies of the climate on other planets such as Earth and Venus.
“As Mars Express has been extended by ESA until at least 2026, this will enable us keep filling this database and refine even further our understanding of Mars atmosphere,” Dr. Tirsch said.
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Daniela Tirsch et al. 2024. Clouds and Storms as seen by HRSC – A catalogue of atmospheric phenomena on Mars. EPSC Abstracts 17, EPSC2024-44; doi: 10.5194/epsc2024-44
Source : Breaking Science News