In The Field

March 26, 2009

LPSC 2009: 40 years strong

lpsc40.jpg This year marks the 40th LSPC conference, and organizers put out a call to see who had attended every single one. Everett Gibson was a 28-year-old freshly minted PhD when he took a job at the Johnson Space Center in 1969, hoping to find water in the very first moon rocks from Apollo 11. At the first LPSC in the spring of 1970, in the long-since-disappeared Albert Thomas Convention Center, he had been working on the rocks for less than a year. Over a hundred teams worldwide had been given rocks to analyse, and the rules were simple. "Each team had to prepare a manuscript for LPSC, and we could not talk to other scientific groups before the meeting," says Gibson. "The world's press were there. Everybody came."
But not everyone came to this year's photo shoot: 40-year veterans Peter Schultz, Jim Head and Larry Taylor were at this year's meeting, but missing. In the picture, sitting in the bottom row, from left to right, is: Everett Gibson, Don Bogard and Gary Lofgren. Standing from left to right are Dmitri Papanastassiou, Don Burnett, Bob Clayton, Larry Nyquist, and Dominic Noto. Since the beginning, Noto has operated a limousine service for the conference, shuttling scientists to and from hotels and airports. He was offered an honorary spot in the photo. "I still come out here and enjoy driving with them," he says.
That's it for me this year, since I have to catch a flight in the morning. I had lots more I was hoping to highlight, but I ran out of time. Hope to see you all next year.

Posted by Eric Hand at 11:31 PM |

LPSC 2009: Squyres speaks

Up at the main Nature News site, I have a new Q&A; with Steve Squyres, the newly selected chair of the next solar system decadal survey.

Posted by Eric Hand at 08:17 PM |

LPSC 2009: Little asteroids on Mars lead to ice

cratercluster.jpg A graduate student on my shuttle bus to the conference center tipped me off to a couple of really cool abstracts, presented on Tuesday and tomorrow. I was all set to push for a story about them. But then a) the authors didn't want to talk to me about it, because they're hoping the work will make a splash in a journal-which-will-not-be-named, and b) I realized that my eagle-eyed editor had, like MRO, already spotted the work, and its novelty, when the authors were presenting it at AGU in December.

But the gist of the work is worth repeating: members of the MRO HiRise team are using fresh impact craters as probes of the subsurface, and are finding ice farther south than anyone has thought possible. Pictured here are the two blue pools of ice exposed after small impacts last summer excavated craters five or six metres across and about 70 centimetres deep. (Little impacts like this happen quite often in Mars' thin atmosphere.)

The authors watched the ice sublimate away over subsequent weeks, and used calculations from that to show that this ice is solid and nearly pure, not just a little bit of pore ice mixed in with the soil. And since these craters lie around 45 degrees north, it means that the subsurface ice that Mars Odyssey spotted (providing the raison d'etre for Phoenix) extends further south than previously thought. And it would support a global atmospheric water content that's higher than what's currently measured -- a sign that subsurface ice on Mars might be in global retreat.

But mostly I just love the idea of using asteroid impacts as a natural, experimental probe. You can spend half a billion dollars to send a robot near Mars' north pole to scoop away soil and expose a trench of ice. Or you can wait for asteroid impacts to do the scooping and trenching for you. Of course, you need to have spent $720 million on MRO, the equivalent of a martian spy satellite.
Image: NASA/JPL-Caltech/University of Arizona

Posted by Eric Hand at 04:37 PM |

LPSC 2009: Ice volcanoes on Titan

hotei.jpg
I have a new story up on the main Nature News site that tries to piece together the growing evidence for an ice volcano at Hotei Arcus, a region of Titan pictured here in an artist's illustration. Bob Nelson and Randy Kirk were already onto Hotei at AGU in December, but they hadn't yet processed everything from two close Cassini flybys on November 19 and December 5. The new data have allowed them a better grasp of the shape of the landscape, which looks volcanic, and Nelson is making the bold claim that, as the region gets brighter, a spectral signature for ammonia (a likely "lava" ingredient) also grows.
Image: JPL/NASA

Posted by Eric Hand at 03:30 AM |

March 25, 2009

LPSC 2009: Prospecting for moon ice

hydrogen.jpg
The Chandrayaan-1 folks had a session yesterday, and people streamed into the room to see what Paul Spudis had to say about ice on the moon. Spudis is an LPI scientist leading the mini-SAR radar instrument on Chandrayaan, which is a prelude to a bigger radar instrument on the Lunar Reconnaissance Orbiter, which will launch in May. Both instruments will search for radar reflections, consistent with ice, in the permanently shadowed craters of the moon's poles; Spudis has been heavily involved in this search for years.
A quick review of history (Spudis has a nice review, colored by his perspective, here): In the 1990s, the Clementine mission got everyone excited by a strange double-bouncing radar reflection from inside some polar craters. Spudis calls this double reflection "CPR" for circular polarization ratio. Blocks of ice -- or rough regolith -- can cause this change in the polarity of the radar signal.
A few years later, Lunar Prospector brought both good and bad news: it detected an excess of hydrogen atoms -- consistent with water in the regolith (shown in the image here). But only at the level of a few percent, which meant that it was uncertain whether it could represent microscopic bits of water in the pores of the soil and rock, or actual chunks of water ice.
And then in a series of papers over the last decade, people like Don Campbell, using ground based radars like Arecibo, weighed in and cast doubt on the Clementine interpretation.
But where Arecibo can only see along the rims of the polar craters, Chandrayaan can look straight down in. Spudis was very coy about what mini-SAR had seen in its first few months of its operations. But he tantalized the crowd with maps of a few small, young-ish polar craters that had high CPR signals inside the rim, but not outside. Normally, you expect the CPR signal to be high both inside and outside the rough fringe of the impact crater. He didn't say if the anomalous result could signal ice. "I don't want to speculate on what we're seeing until we've got these numbers pinned down." Campbell, listening intently in the audience, was also intrigued. "I think it's very interesting, very nice looking data," he says. "But we need to wait and see."
Image: NASA

Posted by Eric Hand at 04:39 PM |

LPSC 2009: Squyres to lead planetary decadal

squyres.jpg Steve Squyres, principal investigator for the Mars Exploration Rovers, has been named the chair of the steering committee for the upcoming planetary science decadal survey, according to David Smith of the National Academies' Space Studies Board. Squyres, of Cornell University, will address LPSC attendees at 12:15 pm on Wednesday.
The solar system decadal survey is like its bigger sibling the astrophysics decadal survey, the latest incarnation of which began last year under the supervision of Stanford University's Roger Blandford. Both are designed to corral and collate the desires of scientists and put them into a prioritized wish-list that agencies and the US Congress then can use to justify their spending.
The last planetary decadal was led by Michael Belton of Belton Space Exploration Initiatives, and was completed in 2003. There will likely be more scrutiny of costs; the two highest priority big missions from the last decadal were a Europa Explorer mission and a Mars Sample Return, missions that are unlikely to happen next decade. The $2 billion Mars Science Laboratory was listed as a 'medium' sized mission to be performed for less than $650 million.
Squyres, who has run one of the most successful missions in NASA history (and one much beloved by the public), ought to be a popular choice. Even the non-Mars people who will complain about a supposed bias for Mars should be consoled by his NASA bio, which describes his past involvement in the Magellan mission to Venus, the Cassini mission to Saturn, and the NEAR mission to the asteroid Eros.
Image: NASA

Posted by Eric Hand at 03:43 AM |

LPSC 2009: Moonface two-face

twoface.jpg The man in the moon always presents us with the same mugshot, because the Earth's tides have locked the moon's spin to ours. But in a talk yesterday, Mark Wieczorek pointed out that not only did it not always have to be this way, but also that there is some evidence that the moon actually did swap its Earth-facing side at least once in the ancient past.
The work builds on a theoretical result in the 1970s from the University of Arizona's Jay Melosh, who showed that there were two equally stable ways in which the face of the moon could freeze toward Earth: the near side, and the far side. A glancing blow from a moderately big asteroid would be enough to do the job. Wieczorek, of the Institut de Physique du Globe de Paris, now shows that if that was the case, there would be a slight preponderance of big impacts on the moon's leading edge (marked 'apex' in the image here), since its orbiting velocity would be added to, rather than subtracted from, the impacting object. Lo and behold, he finds, the oldest impacts cluster around the moon's trailing face -- implying a flip-flop. "It's probably happened several times," he says. Most basin impacts would be big enough for the great switcheroo, but based on chronology, Wieczorek suggests that Smythii would be a likely candidate.
He says the process of a face switch could even start and stop temporary lunar dynamos -- which would be an interesting new mechanism for imprinting magnetic orientations onto lunar rocks.
Melosh was pleased that someone followed up on his theoretical idea, and says it needs to be tested on many of the Jovian and Saturnian satellites. "This suggests that this could be a common process with the other tidally locked satellites," he says.
Image: Wieczorek

Posted by Eric Hand at 12:27 AM |

March 24, 2009

LPSC 2009: Venus or bust

venuslander.jpg With all the fierce debate over sending a NASA flagship mission to Europa or Titan, it's easy to forget that there are other communities waiting in line. Mark Bullock, of Southwest Research Institute, gave a talk describing the results of a major science and technology definition exercise for a future flagship mission to Venus. Given $4 billion to design a mission to be launched by 2025, the team had to figure out the best way to answer the most important science questions (like, does Venus have active tectonics and volcanism?) with technology that's not too far off. The team settled on a particular architecture: an orbiter, two balloons that would last about a month swimming through sulfuric acid clouds, and two landers that would survive a few hours at the lead-melting surface. Here's an artist's impression of the lander after those few hours. Venus is not a forgiving place.
Image: Tibor Balint, JPL

Posted by Eric Hand at 05:04 AM |

LPSC 2009: Dhofar, so far

One more update to the Late Heavy Bombardment story, then I'll shut up about it. I started that story with a discussion of Dhofar 961, a lunar meteorite that many think is the only found meteorite to have been chipped off of the South Pole Aitken Basin, the biggest and oldest basin on the moon, and the one that, once dated, should mark the beginning of the Late Heavy Bombardment. (Statistically, this is long overdue: There are more than 60 lunar meteorites, and South Pole Aitken covers almost 15% of the lunar surface. If meteorites fall from the moon to Earth randomly, then geologists should have around 10 from South Pole Aitken.)
Now, Brad Joliff, of Washington University in St. Louis, Missouri, says he's even more sure it hails from the hole at the bottom of the moon. "We've tightened the argument by using more of the geochemistry that's available."
He used gamma-ray spectrometry data from Lunar Prospector for six main elements that had been tallied for each of hundreds of 5-degree squares on the moon. Comparing Dhofar 961's composition to each of the lunar squares, Joliff found that 9 out of the top 10 possible origins all lie within South Pole Aitken Basin. Next step: doing the painstaking radioisotopic dating work on miniature cores from the Dhofar sample.

Posted by Eric Hand at 04:28 AM |

LPSC 2009: Basins abounding

basins.jpg Last year, I wrote a feature story about the Late Heavy Bombardment, the time, roughly 3.9 billion ago, when the young bodies of the inner solar system were subjected to a beating by asteroids flung in from the outer solar system. The story was partly triggered by an abstract presented here last year: Herb Frey's report that, using topographic data, he could identify some 92 likely impact basins bigger than 300 kilometres across -- twice as many as contained in the canonical database. That meant that the moon -- the 'record plate' for the bombardment, since the relic impact craters and basins are preserved better there than elsewhere -- was hit harder than most thought. And the work somehow made me realize just how hellish the Earth was during that epoch -- probably molten, oceans evaporated, asteroids the size of dinosaur killers casually striking the Earth every few decades or so.
And then in a talk today, Frey, of Goddard Space Flight Center in Greenbelt, Maryland, said that even that was lower bound. By using a crust thickness model, and identifying circular areas where the crust is thin, he can identify 50 more big impact basins unrecognized by topographic alone. That brings the number of basins greater than 300 kilometres up to about 140, he says, three times the standard number. "These should always be considered minimum numbers from now on," he said.
image: Frey, GSFC

Posted by Eric Hand at 04:08 AM |

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