Research Roundup

04 December 2002 |

Astronomers report largest eruption ever seen on Io
Routine monitoring of volcanic activity on Jupiter’s moon Io, now possible through advanced adaptive optics on the Keck II telescope in Hawaii, recently revealed a massive eruption, the largest ever seen on the moon’s surface or in the solar system.

The eruption — which was larger than the city of Los Angeles — occurred in February 2001, but was not reported until Berkeley astronomers completed their image analysis earlier this year. The team, co-led by postdoctoral research associate Franck Marchis and Imke de Pater, professor of astronomy and of Earth and planetary science, described its findings in the Nov. issue of the planetary-science journal Icarus.

“It is clear that this eruption is the most energetic ever seen, both on Io and on Earth,” says Marchis. Material erupting from the Jovian moon covered 1,900 square kilometers, and was far larger than the 1992 Etna eruption in Italy.

“The total amount of energy being released by the eruption is amazingly high,” Marchis says, “with the thermal output from this one eruption almost matching the total amount of energy emitted by all of the rest of Io, other volcanoes included.”

Io, one of four large Jovian moons, is highly volcanic, with high-temperature eruptions that are similar to those occurring on Earth. The 2001 eruption occurred very close to Surt, the site of a large eruption in 1979.
— Robert Sanders

What makes green plants green?
As biologists try to tease out the finer details of the green-plant family tree, one key may lie in the cellular organelle — the chloroplast — that makes green plants green.

The chloroplast is the photosynthetic factory of the plant cell. It contains its own complement of genes that are distinct from the genes in the plant’s mitochondria and from the chromosomes inside the nucleus of the cells.

“The chloroplast genome can be more informative in some ways than the complete nuclear genome, and easier to analyze than plant mitochondrial DNA,” says Brent Mishler, professor of integrative biology and director of the Jepson and University Herbaria.

Mishler is one of nine principal investigators on a new project, supported by a $3-million National Science Foundation grant, to isolate and sequence chloroplast and mitochondrial genomes from 50 to 100 representative plants. It is among the largest of seven collaborative projects funded last month by NSF’s “Assembling the Tree of Life” program.

The research will help biologists determine plant relationships among the more ancient plant groups, including the mosses, algae, and ferns. Some of the key questions to be addressed are how many times green algae from the sea has colonized land, how plants were able to adapt to life on land, and how many times multicellular plants have evolved.

Both chloroplasts and mitochondria are ideal for these studies, says Boore, who is also head of the evolutionary genomics laboratory at the U.S. Department of Energy’s Joint Genome Institute in Walnut Creek. Those parts of plants originated more than a billion years ago, when bacteria colonized early single-celled organisms. Colonization led to a symbiotic relationship and the introduction of photosynthesis, which allows plants to convert sunlight into energy.
—Robert Sanders

How the brain sorts out sensory cues
When the human brain is presented with conflicting information about an object from different senses, it finds a remarkably efficient way to sort out the discrepancies, according to new research led by Berkeley researchers.

The researchers found that when sensory cues from the hands and eyes differ from one another, the brain effectively splits the difference to produce a single mental image. Writing in the Nov. 22 issue of Science, the researchers describe the middle ground as a “weighted average” because in any given individual, one sense may have more influence than the other. When the discrepancy is too large, however, the brain reverts to information from a single cue — from the eyes, for instance — to make a judgment about what is true.

The findings could spur advances in virtual reality programs and remote surgery applications, which rely upon accurately mimicking visual and haptic (touch) cues.

“We found that when subjects grasped an object that felt 54 millimeters thick, but looked as if it were 56 millimeters thick, their brains interpreted the object as being somewhere in between,” said James M. Hillis, lead author of the study and a former graduate student in vision science at Berkeley. Hillis, now a post-doctoral researcher in psychology at the University of Pennsylvania, worked on the research with Martin S. Banks, Berkeley professor of optometry and psychology.

“If the brain is taking in different sensory cues and combining them to create one representation, then there could be an infinite number of combinations that the brain is perceiving to be the same,” Banks says. “The brain perceives a block to be three inches tall, but was it because the eyes saw something that looked four inches tall while the hands felt something to be two inches tall? Or, was it really simply three inches tall? We wanted to know how much we could push that.”
— Sarah Yang


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