Podcaster: Alice Enevoldsen aka Alice’s AstroInfo
Organization: Alice’s AstroInfo
Link : www.alicesastroinfo.com
Description: Gear up for MAVEN’s arrival at Mars with Alice of Alice’s AstroInfo, and brush up for your dinnertable conversations about Mars this weekend. What is MAVEN? What is it studying? What can you expect to hear about as it enters orbit on September 21st?
Bio: Alice Enevoldsen currently volunteers as one of NASA’s Solar System Ambassadors. She has worked in planetariums from 1996 to 2014, and holds degrees in Astronomy-Geology and Teaching. Now she works hard to share her love of the stars and excitement about astronomy with as many people as possible.
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Hello, I’m Alice Enevoldsen, coming to you not-so-live from Alice’s AstroInfo with a podcast about MAVEN, entering orbit around Mars on Sunday.
How are you today? [pause] Neat-o! [pause] I am excited for MAVEN’s arrival at Mars.
About every two years we have a window to send a new mission to Mars. Last November NASA launched MAVEN, the Mars Atmosphere and Volatile EvolutioN mission, a magnifying glass for history detectives here on Earth.
This mission is an orbiter – there is no rover or lander, and it is measuring Mars’s atmosphere with a suite of non-camera instruments on board.
But wait, why do we care about Mars’s atmosphere?
Mars holds a certain magical charm for us. It is one of the most Earth-like bodies in our solar system, and it is easily visible from here. It captures our imagination; stories, stories, and more stories have been written about life on Mars: past, present and future.
Because of this charm, we keep looking at Mars. The more we look, the more we find, and the more questions we unlock.
That’s where MAVEN comes in. It isn’t looking for life. It isn’t following a magical fairy-tale about little green men. It’s asking the question, what happened to Mars’s atmosphere?
Discovery upon discovery points to Mars’s warm, once-wet, thick-atmosphere-d past. The image of Mars’s history becomes clearer with every mission we send. It had water, oceans, and an atmosphere that twinned the Earth’s. It had a magnetic field, like we do (which has been causing plenty of auroras lately). It had the capacity to harbor life. All this is gone, our rovers and landers scraping evidence of it slowly and painstakingly out of the surface rocks, and taking just a few minute and careful samples of the atmosphere at ground level. What happened?
That history, that mystery, is what fascinates us. What happened to Mars’s atmosphere? How long was there enough water and atmosphere to have been habitable?
That’s MAVEN’s job. Gather enough data about Mars’s atmosphere now to figure out what happened then. Once we have that answer we will reveal new questions, which in turn we’ll take a decade designing and launching new missions to investigate. The cycle of science continues.
According to Nick Schneider, the MAVEN instrument lead at LASP (the Laboratory for Atmosphere and Space Physics at University of Colorado, Boulder), there are four simple ways to lose an atmosphere
The first is condensation. If you cool the atmosphere down, it condenses, just like water on the outside of your iced tea glass. This leaves a lot of frozen atmosphere all over the planet, and especially at the poles. Mars has frozen atmosphere at the poles, but not nearly enough to account for the missing thick atmosphere of way back when. So, that’s not where Mars’s atmosphere went.
Next we have chemical reactions and sequestering. The atmosphere reacts to form minerals and get tied up in the surface of a planet. This happens daily on Earth as rust forms on iron, the oceans acidify sucking up the carbon dioxide that we’re producing too much of, etc. (Yes, ocean acidification is a topic for another podcast). Again, we’ve been studying the rocks in detail on Mars’s surface, and we have a pretty good idea of what is there, especially at the very top layer surface. Just like with condensation, there aren’t enough there of the minerals that would be created by sequestering to account for the loss of 90% of that thick pre-historic atmosphere.
Another possibility is thermal escape. You know that heat is just motion. The hotter something gets, the faster the atoms and molecules move on average. Big things, like rockets, need a lot of boost to get going faster than the escape velocity of a planet and get out of that planet’s gravity well. Atoms and molecules are small though, so there are always some moving faster than escape velocity and whizzing off into space, leaving behind an ever-so-slightly less-dense atmosphere. Usually they’re replaced by other atoms and molecules from the planet’s surface, but if the atmosphere gets hot enough, more molecules are lost than replaced, and the atmosphere thins out over time. Lighter molecules (and atoms) escape first, so you can tell if thermal escape is the main factor of a thinning atmosphere by looking at the balance between different types of atoms in the upper atmosphere. From what we currently know about Mars’s atmosphere, this is a possibility for how Mars’s atmosphere thinned.
Lastly, we have solar wind stripping. This one sounds a bit more catastrophic than it is, but it does happen more dramatically than thermal escape. Imagine that the Sun’s solar wind is a giant pressure washer, and Mars’s atmosphere is a nice coating of moss or dust on the brick patio of the planet’s surface. Go ahead: blast it away. Okay, so like I said, it isn’t that fast or catastrophic, but the solar wind is constantly buffeting our planets and their atmospheres. Here on Earth, the magnetic field does a fine job of protecting our atmosphere from being blown away by the wind, but Mars’s magnetic field is long gone. That means its atmosphere is much more vulnerable to the solar wind. Unlike with thermal escape, this strips away charged atoms and molecules more than lightweight ones. This, like thermal escape, is also a great possibility for where Mars’s atmosphere went. It will be easy to tell the difference between this and thermal escape as soon as we have a little bit of data about the concentrations of different atoms and molecules in Mars’s upper atmosphere.
So, come on MAVEN! I can not wait to hear what you’re finding out there.
Once again, I’m Alice Enevoldsen. You can find me online as AlicesAstroInfo on Twitter, Facebook, and www.alicesastroinfo.com.
Keep your eyes high, and if you want to hear more from me next year, go donate to support 365 Days of Astronomy.
Bye! See you later!
End of podcast:
365 Days of Astronomy
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