Destination Phobos

Last month we discussed the Mars Express’ capture of the alignment of Mars two diminutive moons Phobos and Deimos. Now, New Scientist offers an excellent review of the crucial role that Phobos might play in mankind’s future exploration of the solar system in Destination Phobos: Humanity’s Next Giant Leap.

Published in: on January 27, 2010 at 7:12 pm  Comments (1)  

A Panoply of Galaxies

The incredible diversity of galactic shapes and structure (NASA)

The Australian science magazine Cosmos (you’ll find it in the periodicals section) reports in its online edition (Galaxies Shaped By Dark Past) that a pair of astrophysicists have created a model called GALFORM, which simulates galaxy formation in a universe described in one of the dominant cosmological models of the cosmos (the Lambda Cold Dark Matter or LCDM model).

As Cosmos evinces, their “model was able to reproduce the evolutionary history of the universe over its 13.7 billion years. Moreover it not only got the shapes but also the numbers of various galaxies right and the rate at which galaxy mergers occur.

“‘We were completely astonished that our model predicted both the abundance and diversity of galaxy types so precisely,’ said astrophysicist Nick Devereux of Embry-Riddle University in Arizona.’”

The model, now published in the Monthly Notices of the Royal Astronomical Society, further shows that our own galaxy “the Milky Way has a complex past but so far has only undergone minor collisions and the gravitational collapse of its inner disk to form the central bar.”

Published in: on January 27, 2010 at 6:06 pm  Leave a Comment  

Callisto, Ganymede & Comets

Jupiter's second largest moon, Callisto

Four hundred years ago to the month, Galileo trained his telescope on the planet Jupiter and discovered the four largest moons of the solar system’s largest planet.

The very great differences between the two largest of those moons have puzzled scientists for decades. Ganymede, the largest moon in the solar system, and Callisto, are nearly equivalent in size, but only Ganymede has a magnetic field, a highly differentiated composition, and evidence of past tectonics. Now, a pair of scientists from the Southwest Research Institute have proposed in the journal Nature Geoscience that the contrast can be explained by the differential effects of cometary bombardment. (Here is the abstract of their article.)

Here’s how Scientific American explains their thesis in the article Early Cometary Bombardment May Explain the Divergent Path of Jupiter’s Biggest Moons:

“Each time a comet strikes an icy satellite, Barr explains, a portion of the moon’s surface melts from the heat of the impact; the heavier metallic and rocky constituents mixed in sink to the bottom of the melt pool. With enough impacts providing sufficient melting, the sinking rocks’ gravitational potential energy is released as heat, producing more melting, and the separation of rock and ice becomes self-sustaining, a process known as ‘runaway differentiation.’

“During the solar system’s period of intense impacts about 3.8 billion years ago known as the late heavy bombardment, tremendous amounts of cometary material would have been flying around Jupiter and the outer gas-giant planets. Barr and Canup estimate that Ganymede’s proximity to Jupiter, the latter of which acts as something of a gravitational sink, led to Ganymede’s experiencing double the impacts of Callisto, and at higher velocities, to boot. ‘Ganymede gets 3.5 times as much energy in the late heavy bombardment as Callisto,’ Barr says. That energy differential, Barr and Canup realized, could account for Ganymede’s much more complete state of differentiation—the so-called Ganymede–Callisto dichotomy.”

Visit the article in Scientific American, or see the original (subscription required) in Nature Geoscience for greater detail.

Jupiter's largest moon, Ganymede

Published in: on January 27, 2010 at 4:46 pm  Leave a Comment  

Hobbits and Island Dwarfism: An Update

Skull of Homo floresiensis compared with skull of Homo sapiens (Dr. Peter Brown, University of New England)

Since our review of A New Human last January, we’ve been following the remarkable unfolding story of the diminutive people who once populated the Indonesian island of Flores, known popularly as Hobbits. (For excerpts from the book, see here and here; for some of our updates, check here, here and here.)

Now, there’s a new study that buttresses the emerging consensus view that Hobbit represents a separate species in the human lineage.

Specifically, the study supports the notion that “the reduction in brain size during the evolution of Homo floresiensis is not unusual in comparison to these other primates [in the study]. Along with other recent studies on the effects of ‘island dwarfism’ in other mammals, these results support the hypothesis that the small brain of Homo floresiensis was adapted to local ecological conditions on Flores.”

BioMed Central offers a preliminary version of the study with Reconstructing the Ups and Downs of Primate Brain Evolution: Implications for Adaptive Hypotheses and Homo Floresiensis, a 64-page detailed review. For a one-page abstract of the study, look here. You’ll also find much briefer characterizations of the results at EurekAlert! and at Science Daily in Is the Hobbit’s Brain Unfeasibly Small?

Published in: on January 27, 2010 at 11:51 am  Leave a Comment  

State of the Union

The first page of George Washington's very first State of the Union address (Library of Congress)

We’ll be setting the Tivo to record tonight’s State of the Union message while we attend the special talk by Kansas author Jim Hoy tonight. But if you’re going to watch the speech live, you may be interested in some of the past State of the Union addresses delivered by previous presidents.

C-Span offers a State of the Union archive with videos of all the State of the Union speeches by the last four presidents, along with a smattering of earlier videos (President Reagan’s final State of the Union, two of Gerald Ford’s three addresses, and Richard Nixon’s final 1974 speech). You will also find transcripts of all the speeches back through the Truman administration.

Published in: on January 27, 2010 at 10:45 am  Leave a Comment