The dramatic 'Blood Moon' lunar eclipse was big news last week, and if you were up early in the morning to see it, perhaps you also noticed our most mysterious solar system neighbour shining implausibly brightly in the east towards dawn – yes, dazzling Venus!. Along with Mars it is one of the nearest planets to Earth, but unlike Mars we know very little about Venus because of the dense, virtually impenetrable veil that is the planet's atmosphere.
Proposed missions
Perhaps, though, our knowledge is about to receive a boost - NASA has just announced a shortlist of five possible projects for future planetary missions, and Venus is the target of two of them. One, named 'DAVINCI', aims to study the chemical composition of Venus' atmosphere, while the goal of the other, known as 'VERTITAS', is to produce the first high resolution maps of the shape and composition of the planet's surface.
Dense Fog
The problem is the atmosphere of Venus. A number of fly-by space missions have shown that it is an incredibly thick, hot, dense fog formed mainly of carbon dioxide. It is so dense that the surface is permanently obscured to optical telescopes. The only way of peering through it is to use radar, both from spacecraft flying by the planet, and from earth-based radio-telescopes as recently as this year, and remote sensing instruments. These have shown evidence of a volcanic landscape on Venus, with volcanoes and lava flows, as well as numerous craters, but as yet it's not clear whether volcanism is still active there.
The enormous density of the atmosphere also means that at the surface there is huge pressure (92 times that on Earth!), soaring heat (over 400 degrees centigrade), and only dim light. How do we know this? In the 1970's the Soviet Union's Venera series of missions succeeded in sending probes into the Venutian atmosphere, and some landers which managed to reach the surface. The didn't last for long – the heat and pressure soon destroyed them in less than a couple of hours – but this was long enough to obtain interesting data about the composition of the atmosphere and conditions at the surface, including evidence of thunder and lightning, as well a handful of intriguing images of the solid landscape immediately around the landers.
Active volcanoes?
All missions to Venus since Venera have gathered data from afar without venturing to the surface. This method has still resulted in some stunning images and fascinating results. For example, the most recent active mission, ESO's Venus Express, recently produced infrared images of consecutive heating and cooling at certain spots, which, researchers have interpreted as evidence of ongoing volcanic activity, an exciting development if it can be confirmed.
However, it may be a while before scientists have any new data to work with. The Venus Express mission came to an end in November 2014, and the only other Venus mission out there at the moment, the Japanese spacecraft Akatsuki, failed to go into orbit after its launch in 2010 so is not currently producing any data. In November this year a new attempt to insert it into orbit will be made, so fingers crossed for success there. And given the lack of any current NASA mission to Venus, I have high hopes that one of the proposed Venus missions now being considered will finally be given the green light. Watch this space!
http://solarsystem.nasa.gov/news/2015/09/30/nasa-selects-investigations-for-future-key-planetary-mission
NASA Selects Investigations for Future Key Planetary Mission
http://www.esa.int/Our_Activities/Space_Science/Venus_Express/Hot_lava_flows_discovered_on_Venus
Recent news from ESA about the evidence for volcanism on Venus
http://nssdc.gsfc.nasa.gov/planetary/planets/venuspage.html Lots of information about Venus, including a link to a timeline of exploratory missions
http://astronomynow.com/2015/03/10/venus-revealed-in-high-resolution-radar-images-from-earth/
Radıo telescopes observing Venus from Earth
http://news.discovery.com/space/history-of-space/veneras-to-venus-130913.htm
Details and images from the Venera missions
1. NASA http://solarsystem.nasa.gov/galleries/mariner-10s-venus
2. NASA/JPL/ESA http://solarsystem.nasa.gov/galleries/active-volcano-on-venus
3.NASA history office http://solarsystem.nasa.gov/galleries/venera-13-on-venus