What I Learned Today

The discovery of lakes on Titan in 2006 has fueled many imaginations and also inspired a lot of questions. One of those questions was presented today at the LPSC conference by Ralph Lorenz. We’ve observed that these lakes are filled with liquid hydrocarbons, so of course they are a bit different from the lakes we find on Earth. But one curiosity is that in all of our observations, we’ve never seen any evidence of waves in these lakes.

We observe lakes on Titan using radar, to penetrate through its thick atmosphere. Radar returns are sensitive to surface roughness, so waves on lakes (among other things) usually show up quite clearly. (We use this on Earth, too — see ocean features observed by Seasat) But so far, all of our images of Titan lakes have turned out to be entirely flat and glassy — dark surfaces rather than bright ruffled ones.

Why is this? We know there are lakes and we know there are winds, so why no waves? Scientists have attacked this problem by measuring the minimum wind speed needed to kick up waves for (water) lakes on Earth (1-2 m/s) and then adjusting it for Titan’s thicker atmosphere (down to 0.5-1 m/s). Global Climate Models (GCMs) for Titan do suggest that surface winds get above this level during the local summer. Unfortunately, right now it is winter in the south, and there’s where the largest lake (Ontario Lacus) is located. Summer won’t come again until after Cassini’s current Equinox mission ends; the subsequent seven-year Solstice mission might have better luck.

But there could be another reason for the lack of lakes as well. Spectrographic observations of Ontario Lacus suggest that it contains not only ethane and methane but also a lot of dissolved solids (propane and others). These “tarry dregs” would likely increase the lake’s viscosity, making it even harder to ruffle.

Ultimately, until we splashdown into the lake itself, we may not know exactly why the surface stays so calm. Mission concepts such as the Titan Mare Explorer and the Titan Submersible Explorer are designed to do just that.

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More info (LPSC 2-page abstracts, PDF):

• “Why Titan’s Lakes Have Been Smooth So Far — and May Be About to Get Rough,” by Lorenz, Newman, Lunine, and the Cassini RADAR Team
• “Exploring the Seas of Titan: The Titan Mare Explorer (TiME) Mission,” by Stofan, Lunine, Lorenz, Aharonson, Bierhaus, Clark, Griffith, Harri, Karkoschka, Kirk, Kantsiper, Mahaffy, Newman, Ravine, Trainer, Waite, and Zarnecki
• “Titan Submersible Explorer —The Case for Subsurface Sampling of Titanian Lakes,” by Epplery, Waite, Brockwell, Cronenberger, Klaus, and Grayson

My hotel presented me with the opportunity to collect some data about myself. On Monday, I went down to try out their exercise room and spent a while running on a treadmill (the first time I’ve ever used a hotel’s exercise room!). After a while I noticed that the shiny metal bars on the hand-rail actually were designed to measure and report your heartrate. After playing with this a little, of course I started to wonder how my body’s heartrate responded to the speed at which I was jogging.

So today when I went down for some exercise, I also took paper and pen with me. Of course what I wanted was for the machine to continuously record timestamps, speed, and heartrate and to deliver a printout to me at the end (or better, just email me the results). But no such luck, so I had to resort to recording it myself. This turned out to be more awkward than I anticipated; I wanted to record heartrate every 30 seconds, but the machine took 15 seconds just to calculate it, and then I had to fumble and write while jogging. Plus, especially at higher heartrates (or jogging speeds, not sure which was the problem), the machine would report garbage that masqueraded as a real heartrate (like suddenly dropping from 120 to 77 bpm). So in the end I had to do some data cleaning, which always makes me uneasy. But I only removed the obvious outliers and left the rest of the noise in.

The result is surprisingly sensible:

The heartrate values at about 8-15 minutes are not reliable; the machine kept reading low, and an independent test with my jugular and the wall clock suggested I was closer to 150 bpm at that point. (The 150 bpm point at 20 minutes was also from a hand-measurement.) But still, pretty cool! A bit of hysteresis, as you might expect. According to the machine, I burned 196 calories (but it didn’t ask for my weight or mass, so…) and traveled 1.9 miles. And I got to make a graph!

Today was the first day of the Lunar and Planetary Science Conference in The Woodlands, TX (north of Houston). Here are three highlights from today’s sessions:

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Ray Arvidson described sulfate-enriched sand observed by the Spirit rover (“still a rover, not a lander,” he insisted). The sulfates are interpreted as forming in a warm, moist environment created by the ancient volcanism in the area. There are several distinct layers, and the sulfates are found at the bottom, supporting a hypothesis that this area experienced periods of high obliquity (axial tilt) that caused this near-equatorial region to be much colder (and covered in snow).

“Thus while embedded on the side of Scamander crater Spirit has uncovered evidence for two timescales of water-related processes: formation of aqueous deposits associated with early volcanic activity and subsequent continuing redistribution of soluble species associated with orbitally-induced climatic change.”

Two-page abstract (PDF): “Recent Scientific Results from Spirit’s Observations of Sulfate Sands on the Side of Scamander Crater, Columbia Hills, Mars” by Ray Arvidson and the Athena Science Team

By the way, if you’re worried about Spirit, you can browse the latest Free Spirit news. Although it’s been declared a “stationary science platform”, chances are very good that when spring returns and there is more power available from its solar panels, the Spirit team will again see if they can extricate its wheels.

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John Grotzinger provided an update on the upcoming Mars Science Laboratory (MSL) mission (due to launch in 2011) and what landing sites are most attractive in terms of searching for evidence of past life. MSL will be able to search for ancient biosignatures in terms of complex organic molecules, unusual isotope ratios, and unusual rock textures. (I was particularly interested in the last point, since it relates to my work on detecting structural biosignatures by analyzing rock textures.) The original four landing sites being considered are Holden Crater, Mawrth Vallis, Eberswalde Crater, and Gale Crater.

“While each site has its own particular strengths, they share in common two very important attributes: definitive evidence for the former presence of water as seen by either mineralogic or morphologic features (or both), and the presence of prominent stratigraphic sequences, hundreds to thousands of meters thick in some cases, suggestive of sedimentary rocks.”

On January 4, 2010, the MSL Landing Site Steering Committee voted to add two new candidates: Northeast Syrtis and East Margaritifer. Stay tuned for more news as they whittle these finalists down!

PDF: “Mars Science Laboratory, Preservation Potential of Biosignatures and Environmental Records, and the Attributes of Promising Landing Sites” by John Grotzinger

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And finally, I also attended at least one non-Mars talk! Richard Vondrak gave an overview of the current status of the Lunar Reconnaissance Orbiter (LRO), which began its science observations last September. The goals of this mission are to identify safe landing sites, locate useful resources, measure the radiation environment, and test a Synthetic-Aperture Radar (SAR) device.

After a four-day cruise, LRO arrived at the Moon and settled into a commissioning orbit for three months. This highly elliptical orbit took it as low as 30 km above the south pole (periselene, its closest approach to the Moon) and out to 216 km away at aposelene. It then transitioned into a circular orbit (at an altitude of 50 km) for its 12-month nominal science mission. This orbit, interestingly, takes a lot of effort; if LRO does not periodically fire its thrusters to maintain it, the spacecraft will lose 15 km of altitude per month and shortly crash into the Moon. While that was an intentional activity for LCROSS, LRO would prefer to achieve a longer lifetime and even to win an extended mission.

The amount of data being returned by this mission is phenomenal. Due to its relative proximity and a dedicated ground station, LRO is able to return much more data than any Mars mission; in its first 3 months it collected 55 TB (to be released by the Planetary Data Service on March 15) and by the end of a year, it will have accumulated more than 140 TB. By that point it will have depleted its station-keeping fuel and then revert to an elliptical orbit. But no doubt it will still be eager to collect more data!

PDF: “The Lunar Reconnaissance Orbiter at the Midpoint of the Exploration Mission” by Vondrak, Keller, Chin, and Garvin

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I also really enjoyed Ron Greeley’s Masursky lecture, titled “Shifting Sands: Planetary Atmosphere-Surface Interactions.” There are so many truly beautiful aeolian features on Mars!

I just got back from the first meeting of French 140, French Pronunciation, at Pasadena City College. What a blast! We read aloud books that French children use to learn to pronounce words, we carefully repeated vowel sounds, and we sang children’s songs (to work on proper intonation). I’m taking this class to improve my ability to speak the language (having had a nice grammar refresher in last semester’s French Translation class). And so far, truly, it’s pure fun! (I can’t say enough good things about Mme. Pedrini, our professor; I very much enjoyed her class last semester as well.)

I also learned some things today. (Yes, it’s true.) New words:

• bouée: life preserver
• dé: dice
• fusée: rocket
• mûre: blackberry
• pie: magpie
• pile: can
• requin: dolphin
• ruche: beehive
• usine: factory

In terms of pronunciation, I learned: “Vincent” contains two distinct vowel sounds (“ahn” and “ehn”). A single ’s’ between two vowels is pronounced as an English ‘z’, but a double-s is pronounced ’s’; for example, “choisissent” is “shwa-zees”. We also practiced breaking up sentences into units to allow you to lilt the intonation like a real French speaker… although this partitioning seems to be done more by intuition than by tangible rules (mostly breaking on phrase boundaries, though). Here is an example: “La femme de Pa-TRICK | habite à LILLE | avec son ma-RI.” TRICK and LILLE get up-intonation, while RI gets a down-intonation. After doing exercises like this for a while, it starts feeling very sing-song.

And then we launched into a real song, with music to accompany us!

Yes, imagine 29 people in a classroom at 9:30 p.m. singing along to this song. Excellent learning environment. :)

I just returned from two information-packed days at the Get Involved Institute, a California statewide initiative to increase the number of, and contributions of, volunteers at public libraries. I was asked to join the Monrovia Public Library team in attending this conference as a representative volunteer (what a nice compliment!).

We covered a lot of different material, including tips on how to brainstorm what additional roles volunteers might take on in the library, where you might find volunteers with the skills you need, and how to conduct good interviews. But what hit me the most was the way in which the term “volunteer” expanded in my mind. I saw that volunteers could do a lot more than “just” shelve books (which of course is my personal favorite way to contribute). They can manage other volunteers, read to kids en masse at the mall, organize events, organize “ESL Conversation Circles”, conduct surveys about the perception of the library, and more. Several “pilot teams” also attended, who had had the same training last May, and their stories about what projects they’d tackled (and succeeded at) were universally fascinating and motivating. It was great to be part of an enthusiastic, passionate crowd of more than a hundred librarians, volunteer coordinators, library directors, and other volunteers.

We had some hands-on time in which we worked to develop a plan for how to engage volunteers in a new way at our own library. Monrovia’s library is already rather advanced in this respect; our volunteers provide literacy tutoring, offer computer assistance to patrons, re-barcode old books, mend damaged books, sort book donations, staff the bookstore, and so on. But we did identify ways in which the volunteer corps (almost 100 active volunteers) could be better managed, and how to build a volunteer community (with social events and recognition for outstanding achievements). As we worked to develop a position description for a Volunteer Team Leader, the rest of the Monrovia team kept teasing me for my copious note-taking and fast work with the assigned worksheets. “You do know,” our Volunteer Coordinator said, “that you’re going to come home from this with about 20 new jobs for yourself, right?” They jokingly suggested that I quit my day job and just volunteer full-time at the library. :) While I’m not ready for that, I could see myself stepping into a volunteer team leader role, if they need me. I do so love the library!