[meteorite-list] Hot Lava Flows Discovered on Venus

[Ron Baalke]

http://www.esa.int/Our_Activities/Space_Science/Venus_Express/Hot_lava_flows_discovered_on_Venus

Hot Lava Flows Discovered on Venus
European Space Agency
18 June 2015

ESA's Venus Express has found the best evidence yet for active volcanism 
on Earth's neighbour planet.

Seeing the planet's surface is extremely difficult due to its thick 
atmosphere, but radar observations by previous missions to Venus have 
revealed it as a world covered in volcanoes and ancient lava flows.

Venus is almost exactly the same size as Earth and has a similar bulk 
composition, so is likely to have an internal heat source, perhaps due 
to radioactive heating. This heat has to escape somehow, and one possibility 
is that it does so in the form of volcanic eruptions.

Some models of planetary evolution suggest that Venus was resurfaced in 
a cataclysmic flood of lava around half a billion years ago. But whether 
Venus is active today has remained a hot topic in planetary science.

ESA's Venus Express, which completed its eight-year study of the planet 
last year, conducted a range of observations at different wavelengths 
to address this important question.

Volcanic activity on Venus?

In a study published in 2010, scientists reported that the infrared radiation 
coming from three volcanic regions was different to that from the surrounding 
terrain. They interpreted this as coming from relatively fresh lava flows 
that had not yet experienced significant surface weathering. These flows 
were found to be less than 2.5 million years old, but the study could 
not establish whether there is still active volcanism on the planet.  


An additional piece of evidence was reported in 2012, showing a sharp 
rise in the sulphur dioxide content of the upper atmosphere in 2006-2007, 
followed by a gradual fall over the following five years. Although changes 
in wind patterns could have caused this, the more intriguing possibility 
is that episodes of volcanic activity were injecting vast amounts of sulphur 
dioxide into the upper atmosphere.

Now, using a near-infrared channel of the spacecraft's Venus Monitoring 
Camera (VMC) to map thermal emission from the surface through a transparent 
spectral window in the planet's atmosphere, an international team of 
planetary scientists has spotted localised changes in surface brightness 
between images taken only a few days apart.

Brightness changes in Ganiki Chasma

"We have now seen several events where a spot on the surface suddenly 
gets much hotter, and then cools down again," says Eugene Shalygin from 
the Max Planck Institute for Solar System Research (MPS) in Germany, and 
lead author of the paper reporting the results in Geophysical Research 
Letters this month.

"These four 'hotspots' are located in what are known from radar 
imagery to be tectonic rift zones, but this is the first time we have 
detected that they are hot and changing in temperature from day to day. 
It is the most tantalising evidence yet for active volcanism."

The hotspots are found along the Ganiki Chasma rift zone close to the 
volcanoes Ozza Mons and Maat Mons. Rift zones are results of fracturing 
of the surface, which is often associated with upwelling of magma below 
the crust. This process can bring hot material to the surface, where it 
may be released through fractures as a lava flow.

"These observations are close to the limits of the spacecraft's capabilities 
and it was extremely difficult to make these detections with Venus' 
thick clouds impairing the view," says co-author Wojciech Markiewicz. 
"But the VMC was designed to make these systematic  observations of 
the surface and luckily we clearly see these regions that change in temperature 
over time, and that are notably higher than the average surface temperature."

Because VMC's view is blurred by the clouds, the areas of increased 
emission appear spread out over large areas more than 100 km across, but 
the hot regions on the surface below are probably much smaller. Indeed, 
for the hotspot known as "Object A", the team calculate that the feature 
may only be around 1 square kilometre in size, with a temperature of 830 degrees C, 
much higher than the global average of 480 degrees C.

The Ganiki Chasma rift zone was already considered to be one of the most 
recently geologically active regions on the planet, and as the new analysis 
suggests, it is still active today.

"It looks like we can finally include Venus in the small club of volcanically 
active Solar System bodies," says Hakan Svedhem, ESA's Venus Express 
project scientist.

'Our study shows that Venus, our nearest neighbour, is still active 
and changing in the present day - it is an important step in our quest 
to understand the different evolutionary histories of Earth and Venus."

Notes for editors

"Active volcanism on Venus in the Ganiki Chasma rift zone," by E.V. 
Shalygin et al is published in Geophysical Research Letters.

For more information, please contact:

Markus Bauer 
ESA Science and Robotic Exploration communication officer
Tel: +31 71 565 6799 
Mob: +31 61 594 3 954 
Email: markus.bauer at esa.int

Eugene Shalygin
Max Planck Institute for Solar System Research, Germany
Email: shalygin at mps.mpg.de

Wojciech Markiewicz
VMC principal investigator
Max Planck Institute for Solar System Research, Germany
Email: marko at mps.mpg.de

Hakan Svedhem
ESA Venus Express project scientist
Email: Hakan.Svedhem at esa.int