ARLINGTON, Texas, Jan. 2 (UPI) -- A study of GPS satellite orbits suggests the Earth is heavier than thought, perhaps due to a halo of dark matter, a U.S. researcher says.
Dark matter is thought to make up about 80 per cent of the universe's matter, but scientists have been unable to determine much else about it, including its presence in the solar system.
In 2009, researchers at the Institute of Advanced Studies in Princeton, N.J., theorized that observed changes in the speeds of space probes as they flew past the Earth could be explained by dark matter bound by Earth's gravity.
Now Ben Harris at the University of Texas at Arlington used orbiting satellites to see if dark matter might be affecting them.
Using data on the satellites in the U.S. GPS, Russian GLONASS and European Galileo groups, he calculated Earth's mass as "felt" by each satellite.
"The nice thing about GPS satellites is that we know their orbits really, really well," he told NewScientist.com
His research yielded an average figure for the weight of the Earth between 0.005 and 0.008 per cent greater than the value for Earth's mass established by the International Astronomical Union.
This could be explained in there were a disk of otherwise undetectable dark matter around the Earth's equator 120 miles thick and 45,000 miles wide, Harris said.