Venus Express - Additional Findings - Part II

The spacecraft identified 9 hot spots located above trending cells that are estimated to be still active

continents and oceans
New infrared maps of the Southern Hemisphere suggest that Venus once resembled Earth. There was plate tectonic activity on it and it had oceans of water. Findings regarding the chemical composition of the soil also hint at this. The continents had volcanic activity and they were surrounded by oceans. The surface of Phoeba and Regio Alpha are brighter than most parts of Venus' surface and are thought to be the oldest rocks on the planet's surface.

On Earth, such brightness of areas is characteristic of granite rocks that form the continents. Granite is formed when ancient and basaltic rocks intrude into the crust as a result of continental movement. This process is called plate tectonics. Granite rocks are formed by the fusion of water and basalt. The conclusion reached by the researchers is that in the past there were oceans and tectonic activity on Venus. Over the years the water escaped into space and that there is still volcanic activity. Infrared observations can detect temperature changes in the range of 3-20 degrees Celsius. Very low compared to the temperature range of active lava flows. In the infrared map the temperatures range from 442-422 degrees Celsius.

The high temperatures are in the low areas and the low temperatures are in the high areas. This difference in temperatures can be created during volcanic activity or due to differences in the chemical composition of the soil (1).

Volcanic activity

The spacecraft identified 9 hot spots located above trending cells that are estimated to still be active. The solidified lava flows radiating heat on the surface of the ground, have probably undergone little weathering and therefore they should be young in geological terms. Some are 2.5 million years old and most are less than 250,000 years old. It could be that they are similar to volcanic vents and lava flows in limited areas like on Earth. The valleys are warmer than the mountains. Dione and Themes are hot spots that rise to a height of 0.5-2.5 km. It seems that even today there is volcanic activity in them (2). By 2010, 1000 volcanoes had been identified and one of the lava flows was active only decades ago. In the Northern Hemisphere, a lava flow was detected whose temperature is 85 degrees Celsius, hotter than expected. If the lava flowed more than 100 years ago, its temperature should have been lower (3).

The spacecraft was also used for geological investigation of one of the areas near the equator. For this a comparison was made between the Chimon-mana-Tessera area and the nearby Tuuliki volcano and its location S100. The peaks in both places have a similar height above the ground. The volcano was used for comparison with its surroundings. The findings were surprising. At its peak, an unexpected decrease in the amount of material ejected from it was noticed. This decrease corresponds to the presence of felsic rocks - high-energy trending rocks. A decrease in this emission volume was also found in Chimon-mana-Tessera. Since at higher altitudes the winds are faster and stronger, they blow up small grains and reveal the rough material which has a greater emission of material. A question that arose is whether there are indeed felsic rocks on Venus. On a sphere they form in an aqueous environment. There may be other possibilities for the formation of these rocks. What may support this hypothesis is that the Tuuliki volcano formed late on Venus when it could not have had oceans (4).

In 2006-2007, the amount of SO2 in the atmosphere was 1000 particles per unit volume - PPBV (parts per billion by volume). In the following 5 years until 2012, the amount of SO2 is 10 times smaller. A similar process was observed in the 80s of the 20th century by the American spacecraft Pioneer Venus. A steady supply of this gas to the upper atmosphere probably comes from the hot spots. It is important to remember that at high altitudes the ultraviolet radiation of the sun decomposes this gas and its life span is short, less than half an earthly day. The conclusion reached by the researchers is that the rise and fall of the amount of gas at an altitude of 70 km comes from low places. To exclude the volcanic source, the possibility was raised that another source of the gas is plumes of gas rising up. The obvious question is where do they come from? Another question that needs solving is that the amount of gas in the lower atmosphere has remained high and stable for a decade. During this time, no heat increase was observed from the surface which should be consistent with the observed changes. It is possible that the increase in the amount of gas was due to a global circulation of the atmosphere that intensifies the movement of gas from the lower layers of the atmosphere to the higher layers.

During periods when the amount of SO2 is limited in terms of its global distribution, a large part of the gas is found more at the poles than at the equator. This situation reversed in 2006-2007 when the amount of gas was more widespread. It may be that long-term changes in the circulation of the atmosphere caused the gas to rise from the lower layers and changes in the chemistry of the clouds. It is estimated that there are two Halley chambers where the air rises at the equator, reaches the height where the clouds are and moves towards the poles. In these places it sinks towards the ground and returns to the equator. It seems that the changes in the amount of gas between the poles and the equator such as the cyclical increase and decrease in altitudes correspond to fluctuations in the supply of gas from the lower layers in the lower latitudes (5).

Sources

1. "New map hints at Venus' wet, volcanic past" 15.7.2009
http://www.spacedaily.com/reports/New_Map_Hints_At_Venus_Wet-Volcanic_ Past_999.html
2. "Indications of volcanic activity on Venus" 12.4.2010
999.html http://www.spacedaily.com/reports/Indications_ Of _Volcanic _Activity_ On _
Venus _999.html
3. "Evidence of an active Venus found" 25.10.2010
http://www.spacedaily.com/reports/Evidence_Of_An_Active_Venus_Found_999.html
4. "Venus Express unearths new clues to the planet's geological history" 22.5.2012
http://www.spacedaily.com/reports/Venus_Express_Unearths_New_Clues_To_The _Planet_ Geologic_ History_999.html
5. "A new episode of active volcanism on Venus?" 4.12.2012
http://www.spacedaily.com/reports/A_New_Episode_Of_ Active_ Volcanism _On _Venus_999.html