Video: Infrared emissions from the volcanic peak Idunn Mons in the southern hemisphere of Venus reveal recently solidified lava (Video: Ryan Ollerenshaw/Eric DeJong)
Venus鈥檚 namesake may be the goddess of love, but the planet looks more angry than passionate. Two studies that reveal recently solidified lava and what appears to be the largest volcano in the solar system raise the possibility that huge fiery outpourings could still happen there today.
Many planetary scientists had thought Venus was geologically dead, making the Earth the only rocky planet with active volcanism.
Suzanne Smrekar of NASA鈥檚 Jet Propulsion Laboratory in Pasadena, California, and her colleagues have by measuring the infrared 鈥済low鈥� of solidified lava.
Advertisement
Hot rocks
Since the Venusian surface is nearly 480 掳C, it emits infrared radiation. Older volcanic rocks tend to emit less infrared, say the researchers, because carbon dioxide and sulphur dioxide in the planet鈥檚 atmosphere weather the rocks and change their composition.
Smrekar and colleagues used an instrument on the European Space Agency鈥檚 Venus Express spacecraft, which is in orbit around Venus, to monitor infrared radiation at a specific wavelength that penetrates the planet鈥檚 perpetual cloud cover.
They targeted three areas in Venus鈥檚 southern hemisphere that radar and gravity observations by NASA鈥檚 Magellan spacecraft in the 1990s suggested are 鈥渉otspot鈥� volcanic deposits, like Hawaii: the Imdr, Themis and Dione regiones. They found all three areas are especially 鈥渂right鈥� at the infrared wavelength that their instrument could see, which means the rocks there formed more recently.
In the act
Pinning down the exact age of the rocks is tricky, though. It is not clear how quickly the surface is weathered by the atmosphere of Venus. They are no more than 2.5 million years old, Smrekar says, but they could be as young as mere hundreds of years.
鈥淚 think this is way cool,鈥� says at the Southwest Research Institute in Boulder, Colorado, who was not involved in the study. The evidence for recent volcanism 鈥渃hanges our understanding in the sense that now we will probably start focusing on catching Venus in the act of erupting鈥�. Such eruptions would affect the planet鈥檚 atmosphere, clouds and climate, he says.
Big mountain
In another study, which will appear in the May edition of Geology, a map based on radar observations by NASA鈥檚 Magellan spacecraft in the 1990s reveals that a previously known feature on Venus could actually be the largest known volcanic structure in the solar system.
of the University of Minnesota in Duluth re-analysed the area, which includes an oval tectonic feature called Artemis.
Earlier maps of Venus showed Artemis as a raised feature surrounded by a deep ringed trough, 2400 kilometres across in total.
Hansen and colleagues found evidence of lava and a volcanic structure extending well beyond the ring. 鈥溾�� caused by the cooling and contraction of lava extend across an oval 13,000 kilometres wide. Radial fractures, associated with upwelling lava, span 12,000 kilometres.
The structure covers up to one-third of the planet鈥檚 surface. The researchers believe that makes Artemis the largest volcanic feature yet identified in the solar system. It may have been caused by 鈥渁 plume with a much bigger effect on the surface than anyone had envisioned鈥�, she says. 鈥淚t鈥檚 so big it must have come from the core-mantle boundary.鈥�
When the eruption occurred remains unknown, and the volcano is thought to be inactive today.
Journal reference: Science, DOI: 10.1126/science.1186785 (Smrekar et al); Geology, in press (Hansen et al)
