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June 26, 2012
NASA EDGE: Venus Transit with James Garvin


Jim Garvin, Chief Scientist from NASA Goddard Space Flight Center, talks Transit of Venus with NASA EDGE.

FRANKLIN: When Venus passes in front of the Sun, what kind of science can be gained now that you couldn’t gain eight years ago about Venus’ atmosphere?

JIM: In just eight years the technologies of instruments we have to look at planets, including the refurbished Hubble Space Telescope, is in a different state. So, the network of observatories on the Earth, just the networking available through the worldwide web, through the internet; the satellites we have, including a European space agency satellite that’s in orbit around Venus, the Venus Express, built by our friends in the European Space Agency. That, together with this much, more integrated network of observers who can talk to each other through community, social media mechanisms for science allows us to collect more data to look at some very fundamental numbers which were first discovered and measured a hundred or two hundred years ago. Again, I see this transit of Venus as symbolic of where we were more than a century ago to where we’re going with spacecraft that can interrogate these other worlds, even someday around other suns.

FRANKLIN: Tell me about the different layers of the atmosphere of Venus and what can survive and what can’t.

JIM: Venus has one of the biggest atmospheres of any rocky planet in the solar system. In fact, if you compare the atmospheres of Mars, Earth, and Venus, you go Mars little, cold; Earth big, nice, we live there; Venus, gigantic, massive compared to Earth’s, a swirling maelstrom of chemistry, winds and dynamics all of which we really don’t understand. As you start at the top of the atmosphere, you start to hit molecules such as carbon dioxide, escaping hydrogen, and other trace elements. As you move down, you’ll hit a dense cloud deck on Venus that starts somewhere between 40 and 45 km and extends up to about 60 km above the surface. That’s 180,000 to 200,000 feet; much higher than the clouds on Earth that we know and love. That the cloud layer; that multi-deck cloud layer is made up of chemistries that involve sulfuric acid, something that is extremely caustic, not something our spacecraft like, balloons don’t like it, parachutes don’t like it. Then, once you get to about 30 to 35 km above the surface of Venus, the average surface, the atmosphere clears. All the way from there down to the extremely hot surface, it’s clear. In fact, as you fly, you’re limited in what you can see below the clouds by the fraction of this extremely dense CO2 atmosphere. It’s so dense that we measure the density of the atmosphere near the surface of Venus is only about 10 times less dense than liquid water. The carbon dioxide down there is actually a super critical fluid, something very different than we’re use to here on Earth. So, from Venus, as you peel the onion, you get denser, deeper, hotter very quickly. When you go from the cloud deck, roughly the temperature you have in the low altitude clouds here on Earth to the surface where it’s 450° centigrade. Wild and wooly stuff.

FRANKLIN: Volcanoes on top of a surface that is so hot, that just seems to be extreme.

JIM: On Venus, from the Magellan mission, we’ve seen evidence of landforms that remind us of the big volcanoes we have in Hawaii, the big ones on Mars. We see vast rolling plains which look to be like those that could have been formed by the massive flooding of lavas like we think happened on places like Mars, probably on early Earth. We see a very likely volcanic Venus. And recent work by scientists, here in the United States at JPL and other places, suggest that there could be some volcanoes active now; actively erupting even in this hot, crazy planet we know as Venus. If that is happening, Venus may be one of only three places where we see active volcanism of the kind we have on Earth; the Earth, of course, Io, the big moon of Jupiter, and of course, Venus. Now, we have other kinds of things going on at Enceladus, out at Neptune’s moon, Triton but again, these are the kinds of volcanic processes that we know on Earth, critical on Earth, that could be happening now on Venus.

FRANKLIN: How long will we be able to feed off the information we gain during this next transit of Venus, which will be the last in our lifetime?

JIM: This transit of Venus is particularly important because… A. It reminds us how far we’ve come out of the astronomical age into the space age. This is one at the peak of our current capabilities, 50 plus years into the history of NASA. And it reminds us what it might be like 100+ years from now when another generation, another group of people, hopefully, continue exploring our sister world. What we’ll gain from it is the perspective, again, reminding us what is unknown about our sister planet, what is it about transit of planets in front of the sun. And remember, only Venus and Mercury do that, from our perspective on Earth, inside the Earth’s orbit relative to the Sun. What we can learn from that technique as we look out beyond our solar system at other planets around other suns. That’s one of the new fields in astrophysics, taking a census of the exoplanets of our universe. Are there other pale, blue dots like our own priceless world or orange, white dots like Venus, for that matter? That is one of the fundamental questions. How small and interesting can planets get that still sort of behave as big, rocky planets like Earth and Venus because we’re sisters and brothers, Earth and Venus. No other rocky planets are in the same size domain as Earth and Venus. It’s really important to leverage what we can learn from our sister planet.

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