Puzzle about Sudpol ice on Mars solved
The Red Planet, called the God of War by the Greeks and Romans, arouses the strong interest of science, because among all the planets in our solar system it is most similar to the Earth in terms of rotation time, seasons, atmosphere and distance from the Sun.
It has a dark atmosphere, which consists of about 95% CO2 and is very often clouded by dust. Similar to the Earth, Mars is subject to climate fluctuations, largely due to the fact that the orbit of Mars around the Sun has changed slightly in the last millions of years. A change could be determined also regarding the rotation axis, which changed in the last 5 million years constantly between 15° and approximately 35°. As a result, the polar regions are exposed to different levels of solar radiation, a large part of which consists of frozen carbon dioxide (CO2).
Water ice concentration at the south pole of Mars – today and before 21.000 years ago. Image: OMEGA team – F.Montmessin – Service d’Aeronomie du CNRS – IPSL
In order to take a closer look at the Martian atmosphere, a new spacecraft was launched on 2. June 2003 the European probe Mars Express from the Baikonur Space Center, Kazakhstan. The objective of this mission is to clarify what is happening to the water on Mars in order to draw conclusions about the possible origin of life on Mars.
About ½ year after the start of the mission, the OMEGA (Visible and Infrared Mineralogical Mapping Spectrometer) instrument on board made a spectacular discovery: permanent water ice deposits at the south pole of Mars. These are found on overlying rock layers millions of years old and also provided evidence of glacial activity. However, questions about the age and origin remained unanswered.
Mit Hilfe des Omega-Infrarotspektrometers konnten die Wissenschaftler drei unterschiedliche Eistypen auf dem Mars feststellen. Picture: OMEGA team – F.Montmessin – Service d’Aeronomie du CNRS – IPSL
Mars-Sun constellation lets water "fly" from north to south
Now, thanks to the latest data from OMEGA and with the help of sophisticated climate models, scientists have been able to give a possible answer to this question. Analysis of the OMEGA data has shown that the persistent deposits on the Sud Pole consist essentially of three types of ice: Water ice mixed with carbon dioxide ice, kilometer-wide areas of pure water ice, and deposits covered with a dark layer of CO2 ice.
The discovery of ice deposits of the first kind confirmed the previous hypothesis that the CO2 serves as a trap net for water ice. Aber die zwei anderen Eistypen hinterlieben ein grobes Fragezeichen, wie konnte es sich ansammeln und uber diesen langen Zeitraum konserviert wurden?
The sequence of events in the polar south region of Mars since the precession cycle in the period from 21.000 years to the present. Image: OMEGA team – F.Montmessin – Service d’Aeronomie du CNRS-IPSL
Franck Montmessin, of the Service d’Aeronomie du CNRS/IPSL (France)and his colleagues found an explanation:
We believe that the water ice deposits lave back and forth between the two Martian poles (North/South), in a cycle of 51 each time.000 years, a period of time corresponding to the precession of Mars.
Precession is the term astronomers use to describe the wobbling of the planet’s axis of rotation.
To this result came F. Montmessin and his team turning back time in their Mars climate model. The precession was also taken into account in relation to the orbital information. Scientists turned back time by 21.000 years ago, the northern hemisphere of Mars was closest to the sun – a situation that reflected exactly the opposite of today.
The model showed that the water evaporated at the North Pole and was deposited as ice at the South Pole. Each year a millimeter of water ice was deposited at the South Pole, after 10 years.000 years, the ice rose to a thickness of 6 meters. Danach anderte sich die Prazession und die Rotationsachse begab sich langsam in die Position der heutigen Konstellation. Now the water ice migration process was reversed – the water evaporated at the South Pole and returned to the North Pole.
About 1000 years ago, however, this process was stopped for reasons that are still unclear, a layer of carbon dioxide ice was laid over the water ice at the South Pole, preventing further melting.