17 December 2008

AGU Day 2: Venus

Posted by Ryan Anderson

Poor Venus. Even though it is right next door to Earth, it tends not to get much attention. This is because it’s so hot that we can’t last long if we land there, and it’s so cloudy that we can’t study its surface very easily from orbit. It’s a really interesting place though: it is the closest planet in size to the Earth, but it’s climate is drastically different. NASA has quietly begun looking at what it would take to send a flagship mission to Venus, and so the first couple of talks this morning considered what we know about Venus and what the remaining big questions are.


Jim Head gave a whirlwind tour of what we know about Venus. He especially emphasized that the best way to study Venus is in terms of comparative planetology. In other words, how and why is Venus similar to the other planets and how/why is it different? One of the very strange things about Venus is that, unlike Mars and Mercury and the Moon, its surface is not very old. There are some craters, but most of the planet is volcanic plains and tectonic ridges. On the other hand, it doesn’t seem to have active plate tectonics like the earth. Venus seems to be a third, unique case. Its craters are completely randomly distributed. There is no place on Venus that clearly has a higher or lower concentration of impact. This means that the whole surface is about the same age and may imply that it underwent “catastrophic resurfacing”. Obviously, it would be nice to know how such a process works and whether it could happen to earth…

Ellen Stofan gave a good introduction to the Venus Exploration Advisory Group’s (VEXAG’s) list of outstanding questions for Venus exploration. The questions are:

  • Did Venus ever have an ocean?
  • Was its atmosphere ever earthlike?
  • Why does it rotate so slow? (Venus rotates once every 243 days)
  • Why does its atmosphere rotate so fast? (The winds on Venus circulate around the planet about 60 times as fast as the solid planet spins)
  • What caused Venus’s resurfacing, and what was its relation to climate change?
  • Was Venus ever habitable?


This morning I also heard about Japan’s upcoming “Planet-C” Venus Climate Orbiter, which is set to launch in 2010 and will have a nominal mission of 2 years in orbit around Venus. The orbiter will carry 5 cameras to look at Venus in UV, visible, near-infrared and long-wave-infrared. Its main focus is atmospheric dynamics, but will also provide information about lightning, cloud physics, and potential active volcanoes. It will be in an elliptical orbit so that at the farthest point from the planet its orbit will be synchronous with the rotation of the atmosphere.

The final Venus talk of the morning was by Dave Senske about NASA’s study of doing a flagship mission to Venus in the 2020-2025 timeframe. The mission that he described was very ambitious: it would involve two launches! The first would deliver an orbiter and the second would follow with 2 balloons and 2 landers. The balloons would float between 50 and 70 km high in the atmosphere and would last at least a few weeks. The landers would go all the way to the hot, high-pressure surface and would be designed to last at least 5 hours, although Senske mentioned that obviously it would be nice if they lasted for days or months.

A Venus balloon prototype.

A Venus balloon prototype.

The biggest obstacle to landing things on Venus is that we just don’t have technology that can handle the extreme temperatures and pressures. Senske said that their mission concept is pretty conservative in terms of new technology needed, but I still suspect that there will be a lot of difficult problems to overcome to succeed. Of course, this is the sort of thing that NASA engineers love to do, and I bet a lot of the technology needed for a Venus mission would have applications here on Earth.