Across the Universe: Clouds of witnesses
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This column first ran in The Tablet in September, 2016 Scientists communicate with images. We want to know not simply one value, but how each value compares with other values measured in other situations: other times, other samples, other planets. Picturing our data as spots on a grid is worth a thousand numbers. At the 2016 meeting of the Meteoritical Society in Berlin, every paper relied on images with specks of many colors (each color also a different shape, for the the color-blind) representing different sets of data. No number is perfect; no single measurement is perfect. We repeat each measurement tens, hundreds, thousands of times. If you were to plot each measurement you’d get a cloud of dots and hope that the truth is somewhere within that cloud. The better your precision, the tighter your cloud, the better you can guess where the truth may lie. Instead of plotting all the thousands of individual measurements, though, it’s usually sufficient to … Continue reading

Across the Universe: Where’s the olivine?
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This column first ran in The Tablet in July 2014 It was a beautiful theory, while it lasted. Most meteorites are well-compressed lumps of primordial dust and little beads of rock. But some are chips of lava, bits of some small asteroid that melted and sorted itself into a small iron core and a crust of frozen basaltic lava. We’ve even seen one such asteroid: the spectra colors of Vesta (the brightest, and second-biggest, of the asteroids) uniquely match these basaltic meteorites [in particular, the Howardite-Eucrite-Diogenite meteorites known familiarly as the HED meteorites]. When a mixture of various minerals gets hot, as inside a volcano, only some of those minerals melt; they make the lava that erupts to the surface, leaving behind other unmolten minerals deep below the volcano. These meteorite lavas should behave the same way. During my student days in the 1970s, we calculated that that for every basaltic meteorite, there should be about four times as much … Continue reading

Across the Universe: Dawn of My Belief
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This column first ran in The Tablet in June 2011 As a graduate student in 1976 I gave a paper to the Meteoritical Society about a theory that I (and my thesis advisor) had developed concerning a rare class of meteorites which appeared to be bits of lava from the surface of an asteroid. While most asteroids are collections of metal and rock, we knew that some of them must have melted; for one, asteroid Vesta’s infrared colors exactly matched the spectra of these basaltic meteorites. Our work determined that for every gram of lava in these meteorites, there should have been another nine grams of residue in its parent asteroid. After my talk, a grand old man of the field approached me. “If these meteorites come from an melted asteroid,” he asked, “lavas flowing to the top and residue in the center, then once it was broken into meteorites, shouldn’t we have we seen nine times as many meteorites from … Continue reading

Br Guy Diary: February 22, 2015
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This week has been a week of travel, with a bit of science and a lot of outreach. I experience a blizzard in Boston and warm, dry days in California; talked about Vesta and ET’s; and met some alpacas… I arrived in Boston for the Boskone SF convention just before the snow. I also got a morning’s work in, speaking with Cy Opeil at Boston College. He has a lab set up that we’re collaborating with to measure meteorite thermal and physical properties at temperatures down to near absolute zero. The convention was a whirlwind – and that was just the blizzard outside! I actually never left the hotel, given the weather, which meant I stayed warmer than I usually do at that convention. Monday my flight left on time, and so by Monday evening I was in Merced, California, where over the next three days I gave four presentations at the University of California Merced. Great students, great conversations. I’ve … Continue reading

Br Guy’s Diary: December 31, 2014
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My plan is to post regular updates, about once a week I hope, on my current work and the doings at the Vatican Observatory. This might give the members of our Sacred Space an idea of what our day to day life is like. Let me know if you enjoy these entries! This week: revising Vesta, talking Galileo, and voyages near and far. Science: The science on my agenda this month is to resubmit our paper on Vesta. For the past couple of years I have been working with a team of scientists in Italy, Switzerland, Greece, Russia and Japan to look over the likely internal structure of asteroid 4 Vesta in light of the new data we have gotten from NASA’s Dawn spacecraft. Our paper was written up and submitted in early September; the editors of the journal we sent it to, Icarus, passed it out to a couple of other scientists who checked it over for errors and other … Continue reading

New Worlds in 2015: Missions to Ceres and Pluto
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Among the spacecraft now exploring the solar system are two that, if all goes well, will give us our first close-range views of distant worlds. Having orbited Vesta for over a year, then departed, NASA’s Dawn spacecraft is presently cruising through the asteroid belt for a rendezvous with the largest asteroid, Ceres. In April, Dawn’s ion-propulsion thrusters will ease it into orbit, beginning a prolonged campaign to study Ceres. The low density of the 950-km-diameter asteroid suggests that it may contain frozen water in abundance. It may be a specimen, or at least a relative, of the kind of protoplanets that merged long ago to form the major planets. As for Vesta, previous explanations of its nature do not match the wealth of new data on its geochemical composition. Following Dawn’s extended visit, studies of Vesta and similar bodies are entering a new era. Meanwhile, the New Horizons spacecraft is nearing its own target, Pluto. Launched by the U.S. in … Continue reading