On the horizon: News from the frontiers of science

The largest exoplanet is discovered, reviving ancient frozen bacteria, new findings about primitive man.

Scientists spot cosmic puffball

Another star, another planet, and this one's an oddball.

Astronomers have announced that they've found a puffball of a planet (TrES-4) orbiting a star some 1,400 light-years from Earth in the constellation Hercules. The planet, about 70 percent larger than Jupiter, is the largest exoplanet yet found. It orbits its sun once every 3.5 days at a distance of about 4.5 million miles. And it's hot – about 2,300 degrees F.

But if the planet is big, it's also a relative fluffball. The team calculates that the planet's gravity is so weak that its atmosphere may trail away from it like a comet's tail. The researchers estimate that the orb has the density of balsa wood or volcanic pumice.

And therein lies a mystery, notes Edward Dunham, a researcher at the Lowell Observatory in Flagstaff, Ariz., and a member of the team. The planet falls into a category known as superheated gas giants, or "hot Jupiters." Current theories about how these kinds of planets form can't explain how something so voluminous could have such a low mass, and hence, low density. The results are set to be published later this year.

DNA popsicles

The alien life forms that lurk in some people's refrigerators have nothing on Kaye Bidle's microorganisms. His come from Antarctic glaciers and range in age from 100,000 to 8 million years old. The question: Can these frozen microbes be revived?

The short answer, according to the Rutgers University marine scientist is: Yes, but....

He and colleagues from the US and South Korea found the 100,000 year old microbes could be cultured, and their populations doubled each day. But the 8 million-year-old microbes grew far more slowly. Their populations doubled every 70 days. And their strands of DNA – only 0.007 percent the length of a typical bacterium's DNA – had deteriorated so badly than even after they grew, the team couldn't identify them.

The implications? First, it's highly unlikely that bacteria hitching rides on comets could have helped seed Earth with life. Bacteria in Antarctica are exposed to high levels of cosmic rays. Cosmic rays would have sliced and diced the DNA of comet-riding bacteria as well. Second, bacteria cultured from the younger ice implies that their DNA could periodically be released into the environment and taken in by other bacteria. Melting of such "DNA Popsicles" between ice ages could have helped speed the pace of microbial evolution, the team speculates. The results appear in the current issue of the Proceedings of the National Academy of Sciences.

New views on primitive man

Anthropologists trying to trace human evolution have long peered at hominid fossils and asked: Who's your daddy? Now, it appears that it may not be who they thought it was.

For instance, it's long been held that Homo sapiens evolved from an earlier hominid species, Homo erectus. And Homo erectus evolved from Homo habilis. But scientists working in Kenya now say they have found strong evidence that H. erectus and H. habilis occupied the same hood for half a million years or so. So, they say, it's unlikely that H. erectus evolved from H. habilis. Instead, the two appear to have shared a common ancestor between 2 million and 3 million years ago.

The evidence comes in the form of two fossils: a 1.44 million year old jawbone from H. habilis and what the team says is an impressively preserved skull of an 1.55 million year old H. erectus – both from Kenya's Lake Turkana Basin. Lineage is not the only point at issue. The team says that H. erectus may not have been as human-like as previously believed. They base this on the small size of the H. erectus skull they found. When added to H. erectus skulls already studied, the diversity of sizes almost rivals that found in gorillas, where males tend to be much larger than females, the team says. This is a trait that would imply that H. erectus is more primitive than past studies suggest. The results appear in today's issue of the journal Nature.