In the 1970s, orbiter missions around Mars revealed that during southern spring, large areas near Mars's south pole became much darker than the rest of the seasonal ice cap. How could this area be in the polar region and not be covered in bright ice? Intrigued, planetary scientists called the area the 'cryptic region' of the south seasonal cap.
The mystery deepened in the late 1990s when new observations showed that the temperature of the cryptic region was close to -135º Celsius. At that temperature, carbon dioxide ice had to be present. So, scientists developed the idea that a one-metre-thick slab of clear carbon dioxide ice covered the cryptic region, allowing the dark surface underneath to be seen.
However, the new observations from Mars Express's OMEGA instrument show that this interpretation cannot be correct. OMEGA measures the amount of visible and infrared radiation bouncing off the Martian surface. In so doing, it detects minerals and ices on the surface by charting the specific wavelengths of radiation they absorb.
Carbon dioxide ice (dry ice) absorbs infrared light strongly at specific wavelengths. "We see only weak absorptions in the infrared, which would indicate little carbon dioxide ice in the cryptic region," says Yves Langevin, Institut d'Astrophysique Spatiale, Orsay, France, who led the analysis of the OMEGA results.
The only way to reconcile the apparently conflicting observations is that there is indeed a thick slab of dry ice in this area, but its surface is so heavily covered by dust that few of the Sun’s rays make it to the deeper layers and back again.
How does the dust get on top of the slab? The answer could be provided by the mysterious markings that dot the cryptic region. Known as spots, 'spiders' and 'fans' depending upon their shapes, they were discovered in 1998–1999 by NASA's Mars Global Surveyor.
Planetary scientists believe they are caused by sunlight passing through the clear ice and heating the soil underneath. This causes pressure to build up in carbon dioxide bubbles below the ice until a geyser erupts throwing dust onto the surface, creating the spots and fans. In this model, the spiders result from erosion of the underlying surface by rapid gas flows below the ice. Langevin believes that this process could significantly contribute to the dust contamination of the icy surface, which OMEGA observed.
"In terms of physics, this is a straightforward process and would go a long way towards explaining our observations," says Langevin. However, there are major questions remaining, such as why are spiders, spots and fans only observed in a small fraction of the cryptic region? And why are areas not covered by spots and fans already relatively dark.
To clarify these points, Langevin must wait until the next southern spring equinox on Mars, in 2007. During the long winter, the Sun cannot be seen from the south pole and a pristine layer of ice should build up over the cryptic region. Langevin wants to observe the cryptic region close to the spring equinox, before the Sun has touched it and started the venting process. This will tell him when the dust geysers form and whether they are the ice slab’s only source of dust contamination.
So, whilst not as cryptic as it once was, Mars's south polar region still has a few mysteries left.
Agustin Chicarro | alfa
NASA's Fermi catches gamma-ray flashes from tropical storms
25.04.2017 | NASA/Goddard Space Flight Center
DGIST develops 20 times faster biosensor
24.04.2017 | DGIST (Daegu Gyeongbuk Institute of Science and Technology)
More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.
Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...
Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.
"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...
The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.
Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...
The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...
Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.
Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...
20.04.2017 | Event News
18.04.2017 | Event News
03.04.2017 | Event News
26.04.2017 | Earth Sciences
26.04.2017 | Health and Medicine
25.04.2017 | Physics and Astronomy