Hot Lava Flows discovered on Venus

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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.ba...@esa.int

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

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

Hakan Svedhem
ESA Venus Express project scientist
Email: hakan.sved...@esa.int