Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Ice clouds put mars in the shade

17.01.2008
Until now, Mars has generally been regarded as a desert world, where a visiting astronaut would be surprised to see clouds scudding across the orange sky. However, new results show that the arid planet possesses high-level clouds that are sufficiently dense to cast a shadow on the surface.

The results were obtained by the OMEGA Visible and Infrared Mineralogical Mapping Spectrometer instrument on board ESA’s Mars Express.

Mars is not entirely a haven for Sun worshippers. Clouds of water ice particles do occur, for example on the flanks of the giant Martian volcanoes. There have also been hints of much higher, wispy clouds made up of carbon dioxide (CO2) ice crystals. This is not too surprising, since the thin Martian atmosphere is mostly made of carbon dioxide, and temperatures on the fourth planet from the Sun often plunge well below the ‘freezing point’ of carbon dioxide.

Now, a team of French scientists has shown that such clouds of dry ice do, indeed, exist. Furthermore, they are sometimes so large and dense that they throw quite dark shadows on the dusty surface.

“This is the first time that carbon dioxide ice clouds on Mars have been imaged and identified from above,” said Franck Montmessin of the Service d’Aeronomie, University of Versailles (UVSQ), lead author of the paper in the Journal of Geophysical Research. “This is important because the images tell us not only about their shape, but also their size and density.

“Previously, we had to rely on indirect information – for example, from the SPICAM instrument on board Mars Express - to find out what the clouds are made of. However, it is very difficult to separate the signals coming from the clouds, the atmosphere and the surface.”

Data from the SPICAM Ultraviolet and Infrared Atmospheric Spectrometer indicated that any high altitude clouds are not very thick and made up of much smaller particles, but the CO2 clouds detected by OMEGA are very different. Not only are they surprisingly high – more than 80 km above the surface – but they can be several hundred kilometres across. They are also much thicker than expected. Instead of looking like the wispy ice clouds seen on Earth, they resemble tall convectional clouds that grow as the result of rising columns of warm air.

Even more surprising is the fact that the CO2 ice clouds are made of quite large particles - more than a micron (one thousandth of a millimetre) across – and they are sufficiently dense to noticeably dim the Sun. Normally, particles of this size would not be expected to form in the upper atmosphere or to stay aloft for very long before falling back towards the surface.

“The clouds imaged by OMEGA can reduce the Sun’s apparent brightness by up to 40 per cent,” said Montmessin. “This means that they cast quite a dense shadow and this has a noticeable effect on the local ground temperature. Temperatures in the shadow can be up to 10°C cooler than their surroundings, and this in turn modifies the local weather, particularly the winds.”

Since the CO2 clouds are mostly seen in equatorial regions, the OMEGA team believes that the unexpected shape of the clouds and large size of their ice crystals can be explained by the extreme variations in daily temperature that occur near the equator.

“The cold temperatures at night and relatively high day-time temperatures cause large diurnal waves in the atmosphere,” explained Montmessin. “This means there is a potential for large-scale convection, particularly as the morning Sun warms the ground.”

Bubbles of warm gas rise above the surface and when they reach high levels they become cold enough for CO2 to condense. This process releases latent heat, which causes the gas and the ice particles to rise even further.

What are the particles around which the CO2 ice condenses? On Earth, cloud droplets form around tiny nuclei – often particles of dust or salt. On Mars, the answer remains uncertain. One possibility is that Martian dust is carried to high altitudes. Another potential source of condensation nuclei is particles left behind by micrometeorites entering the upper atmosphere. Or the nuclei may simply be tiny crystals of water ice carried aloft on the thermal updraughts.

“This discovery is important when we come to consider the past climate of Mars,” said Montmessin. “The planet seems to have been much warmer billions of years ago, and one theory suggests that Mars was then blanketed with CO2 clouds. We can use our studies of present-day conditions to understand the role that such high level clouds could have played in the global warming of Mars.”

Agustin Chicarro | alfa
Further information:
http://www.esa.int/SPECIALS/Mars_Express/SEM1DV3MDAF_0.html

More articles from Physics and Astronomy:

nachricht Measured for the first time: Direction of light waves changed by quantum effect
24.05.2017 | Vienna University of Technology

nachricht Physicists discover mechanism behind granular capillary effect
24.05.2017 | University of Cologne

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: A quantum walk of photons

Physicists from the University of Würzburg are capable of generating identical looking single light particles at the push of a button. Two new studies now demonstrate the potential this method holds.

The quantum computer has fuelled the imagination of scientists for decades: It is based on fundamentally different phenomena than a conventional computer....

Im Focus: Turmoil in sluggish electrons’ existence

An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.

We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...

Im Focus: Wafer-thin Magnetic Materials Developed for Future Quantum Technologies

Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.

Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...

Im Focus: World's thinnest hologram paves path to new 3-D world

Nano-hologram paves way for integration of 3-D holography into everyday electronics

An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...

Im Focus: Using graphene to create quantum bits

In the race to produce a quantum computer, a number of projects are seeking a way to create quantum bits -- or qubits -- that are stable, meaning they are not much affected by changes in their environment. This normally needs highly nonlinear non-dissipative elements capable of functioning at very low temperatures.

In pursuit of this goal, researchers at EPFL's Laboratory of Photonics and Quantum Measurements LPQM (STI/SB), have investigated a nonlinear graphene-based...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Marine Conservation: IASS Contributes to UN Ocean Conference in New York on 5-9 June

24.05.2017 | Event News

AWK Aachen Machine Tool Colloquium 2017: Internet of Production for Agile Enterprises

23.05.2017 | Event News

Dortmund MST Conference presents Individualized Healthcare Solutions with micro and nanotechnology

22.05.2017 | Event News

 
Latest News

Physicists discover mechanism behind granular capillary effect

24.05.2017 | Physics and Astronomy

Measured for the first time: Direction of light waves changed by quantum effect

24.05.2017 | Physics and Astronomy

Marine Conservation: IASS Contributes to UN Ocean Conference in New York on 5-9 June

24.05.2017 | Event News

VideoLinks
B2B-VideoLinks
More VideoLinks >>>