TUCSON, Oct. 8 (UPI) -- U.S.-led scientists estimate the human immunodeficiency virus began spreading between 1884 and 1924, about 30 years earlier than prior estimates.

Led by University of Arizona Assistant Professor Michael Worobey, the researchers discovered the world's second-oldest genetic sequence of a strain of HIV known as HIV-1 group M. The sequence was recovered from a lymph-node tissue biopsy taken in 1960 from a woman in the Democratic Republic of the Congo.

The oldest known HIV-1 group M genetic sequence is from a 1959 blood sample of a man also from central Africa. The scientists said a comparison of the 1959 virus and the 1960 virus led them to conclude the genetic divergence between the HIV sequences required more than 40 years.

The researchers said they also used other HIV-1 genetic sequences to estimate probable rates of the evolution of the HIV-1 group M strain. According to their calculations, HIV began spreading among humans between 1884 and 1924 -- about the same time large urban population centers were being established in west-central Africa.

That, said the scientists, is also the region where the HIV-1 group M strain is thought to have emerged.

The study appears in the journal Nature.

Arctic storms and sea ice drift are linked

GREENBELT, Md., Oct. 8 (UPI) -- The U.S. space agency says the rising frequency and intensity of Arctic storms during the last half century is accelerating the rate of Arctic sea ice drift.

National Aeronautics and Space Administration researcher Sirpa Hakkinen of the Goddard Space Flight Center and colleagues from the Woods Hole Oceanographic Institution and the Arctic and Antarctic Research Institute not only linked climate to storminess, but their data also connect increasing trends in arctic storminess and the movement of arctic ice.

"What I find truly intriguing about confirming the link between the rise in storminess and increased sea ice drift is the possibility that new sinks for carbon dioxide may emerge from this relationship that could function as negative feedback for global warming," said Hakkinen.

The researchers analyzed 56 years of storm track data and confirmed an accelerating trend in storm activity in the Arctic from 1950 to 2006.

Acknowledging ice as a harbinger of climate change, they then analyzed ice drift data from the same period. The team found the pace of sea ice movement from Siberia to the Atlantic Ocean accelerated in both summer and winter during the period.

The findings are reported in the journal Geophysical Research Letters.

Colon cancer linked with obesity, genetics

BIRMINGHAM, Ala., Oct. 8 (UPI) -- U.S. medical scientists say they are the first to demonstrate a genetic linkage between obesity and the risk of colon cancer.

University of Alabama at Birmingham researchers say their finding could lead to greater accuracy in testing for the disease and might improve efforts to ward off colon cancer with obesity-fighting activities, such as exercise, weight loss and healthy eating.

It has already been proven obesity is influenced by genetics, and colon canceralso is influenced by genetics. The new study is the first to make a three-way scientific connection between genetic variation, obesity and colon cancer risk, the researchers said.

"Our hope is that we can significantly improve the screening and early detection for this disease, and open new avenues for better understanding the genetic and lifestyle factors that influence colon cancer risk," said Dr. Boris Pasche, lead author of the study.

The findings are published in the Journal of the American Medical Association.

New, smaller satellites are developed

ANN ARBOR, Mich., Oct. 8 (UPI) -- U.S. scientists say they are developing a satellite about the size of a loaf of bread that will be deployed to study space weather.

The National Science Foundation-funded project called Radio Explorer, or RAX, is being led by the University of Michigan and the SRI International Corp., a California independent research and technology development organization.

The satellite, called CubeSat, is to be the first free-flying spacecraft, and will be built, in part, by members of the university's Student Space Systems Fabrication Laboratory.

CubeSats are approximately 4-inch cube-shaped devices that launch from inside a P-Pod -- a special rocket attachment developed by California Polytechnic State University and Stanford University.

The RAX satellite will essentially be made of three CubeSats and will measure the energy flow in the Earth's ionosphere, where solar radiation turns regular atoms into charged particles.

"This project will help us better understand space weather processes, how the Earth and sun interact and how this weather produces noise in space communication signals -- noise that translates to lower quality telecommunications capabilities and error in GPS signals," said Assistant Professor James Cutler, a co-principal investigator with physicist Hasan Bahcivan of SRI.

RAX is scheduled for launch in December.