A comet's odd orbit hints at hidden planet

Far beyond the solar system's nine known planets, a body as massive as Mars may once have been part of our planetary system–and it might still be there.

Although the proposed planet would lie too far away to be seen from Earth, its gravitational tug could account for the oddball orbit of a large comet spotted in the outer solar system a year ago.

Known as 2000 CR105, the comet moves about the sun in a much more elongated pathway than originally thought, astronomers now find. Observations over the past year by Brett Gladman of the Observatoire de la Cte d'Azur in Nice, France, and his colleagues show that the comet's orbit takes it further than 200 astronomical units (AU) from the sun and as close as 44 AU. One AU equals the Earth-sun distance of about 150 million kilometers.

Such an oblong orbit is usually a sign that an object has come under the gravitational influence of a massive body. But 2000 CR105, which may be an escapee