Spacecraft to observe two Saturn moons

PASADENA, Calif., Dec. 9 (UPI) -- NASA says its Cassini spacecraft is set to make its closest swoop over Saturn's moon Dione and will also scrutinize Titan, the ringed planet's largest moon.

The spacecraft will approach to within 61 miles of Dione at about 4:30 a.m. EST Dec. 12 to measure variations in the moon's gravity and look for heat emissions along fractures on the moon's surface, to gain understanding of its internal structure, a NASA release said Friday.

Cassini will examine whether Dione, like another Saturnian moon, Rhea, possesses a tenuous atmosphere.

After its examination of Dione, Cassini will approach to within about 2,200 miles of Titan surface Dec. 13 to make measurements to understand how the seasonal transition from spring to summer affects wind patterns in the atmosphere near Titan's north pole.

Cassini will re-examine an area of Titan where its imaging science subsystem saw sudden and dramatic surface changes last year in the moon's early northern spring -- possibly the result of rainstorms -- NASA said.