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Lake On Titan Winks From a Billion Kilometers Away
The Bad Astronomer writes "NASA's Cassini spacecraft took an image of Saturn's giant moon Titan earlier this year that serendipitously provides proof of liquid (probably methane) on its surface. The picture shows a glint of reflected sunlight off of a monster lake called Kraken Mare (larger than the Caspian Sea!). Scientists have been getting better and better evidence of liquid methane on Titan, but this is the first direct proof."
Prior to this, the main evidence that Titan might have liquid methane was based on the reflection of radio waves detected by the Cassini probe. In particular, there were discrepancies between what one would expect and what was observed in the percentage of reflection in the ELF range (about 2 to 30 Hz). This discrepancy suggests some form of boundary layer, such as a boundary between liquid and solid methane or between liquid methane and some other solid substance. There's also a lot of evidence for a large internal methane sea under the solid surface. We still know very little about Titan. We've only sent a single probe (Huygens) actually dedicated to investigating it. However, even Huygens wasn't much and was just a part of the larger Cassini mission. The next scheduled mission is the TSSM (Titan Saturn System Mission) (http://en.wikipedia.org/wiki/Titan_Saturn_System_Mission http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=44033) which will focus a lot more on Titan. Hopefully a lot of the mysteries about the moon will then be answered.
Titan is routinely used as an example of a moon that might have life. Unfortunately, if there is any life, it is almost certainly microbial. So no one is appreciating the view from the planet.
Just be glad it's not "Lake on Titan Winks from 621 Million Miles Away"
Or "Lake on Titan Winks from 4.97 billion Furlongs Away"
Or "Lake on Titan Winks from 10^-12 Diopters Away"
We know that Titan has a lot of methane. The main reason is that the radiation it gives off is consistent with methane. In particular, we can use spectroscopy to confirm that the light given off is highly consistent with methane reflecting light from the sun. See http://en.wikipedia.org/wiki/Spectroscopy. We have evidence for the methane nature both in the visible range, infrared range and certain other ranges that is consistent with methane and not much else. Moreover, methane is very stable and fairly common (as chemicals go) so even if we didn't have very good spectroscopic data, it would be the most likely guess.
Depends on whether those are British billions or normal billions.
http://www.askoxford.com/asktheexperts/faq/aboutwords/billion?view=uk
This image was taken by Cassini, the US probe currently orbiting Saturn. http://www.nasa.gov/mission_pages/cassini/multimedia/cassini20091217.html Issues in our own atmosphere thus could not impact this. And if you meant that Titan might have strange atmospheric behavior causing this, that's almost as unlikely. The size of this event is much larger than almost any weird atmospheric event (which are normally at most a few hundred meters large at the very largest, rather than many kilometers across. Moreover, this picture isn't the only data point. The data was consistent with specular reflection over all observed wavelengths (both visual and near infrared). So you would need to posit an extremely large event that happened to precisely duplicate what we'd expect to see in reflection. That's remotely possible, but not at all likely. There's never "proof" in science. Proof is for mathematics and alcohol. But this is very strong evidence for the presence of a large body of liquid methane on the surface of Titan.
Methane is the precursor to organic molecules, in a more general sense, not the result of biological processes. When you're the simplest combination of carbon (what, the fourth most abundant element in the universe?) and hydrogen (the most abundant element), it's hard to argue that your existence requires biological processes. (Particularly as methane is found everywhere volatiles can be found in our solar system and outside of it.)
Perhaps you're confused by the fact that methane on Earth is usually the result of biological activity? That's because in our peculiar atmosphere, methane can't survive long before oxidation.
The methane is believed to come from geological processes and not from life.
No matter how you say it, it's wrong. It winks from 200,000 kilometers away. The rest of the distance was just data transfer.
Actually it's one and a half hour away. At light' speed, I mean.
I happen to have been tech resp. of the european Huygens probe that Cassini brought to Titan, and what I remember the most from the time of Huygens descent and landing years ago, is this feeling that all the active descent has *already* happened, while here on Earth we didn't yet have received the first bits of info, radiowave that were still into the travel.
Indeed that was a very real way of measuring distance. Saturn definitely is not close...
Hervé S. (now back on more conventional Earth observation spacecraft designs ;-)
Herve S.