What's up in the solar system for the week of May 5

Here's what's happening on active planetary missions this week.

At Saturn, Cassini is at apoapsis today, beginning rev 67 (which will actually be its 68th complete orbit of Saturn). Like revs 63-66, rev 67 will a 9.6-day, steeply inclined orbit around Saturn. It is currently on the north (unlit) side of the rings, and will cross to the lit side at 00:05 UTC on Saturday, May 10, reaching periapsis two hours later. It's headed for a targeted (1,000-kilometer) flyby of Titan on Monday, and the gravity assist will make its orbit even tighter and steeper. No targeted flybys or more distant approaches to the major moons will occur this week. Last week's image releases all focused on storms on Saturn and patterns induced in the rings by shepherding moons.

On the surface of Mars, it is late autumn in the southern hemisphere (Ls 68°), sol 1,542-3 for Spirit and sol 1,522-3 for Opportunity. Spirit is still parked on the edge of Home Plate, in the same position it has occupied since sol 1,464 (February 15), with its solar cells pointed northward toward the winter sun. Opportunity is sitting on the slope of Duck Bay, with its wheels dug in to a patch of sand, diagnosing a problem with the shoulder joint on its robotic arm. A. J. S. Rayl filed her monthly report on the status of the rovers last week. Phoenix is zeroing in, now only 20 days from its May 25 landing. The April 30 weather update from the MARCI camera on Mars Reconnaissance Orbiter observed a large dust storm at the north polar cap edge, just north of the Tharsis and Arcadia regions, which "lofted diffuse dust onto the perennial cap for several days." The rover sites remain fairly dust-free, experiencing "slightly cloudy skies but no dust storm activity."

Last week's image releases from the Mars Odyssey mission focused on beautiful patterns in images from Mars orbit: intersecting patterns of linear ridges in Noachis terra, an oddly linear pattern of erosion in Elysium planitia, fractal terrain in Elysium through which winds a volcanic channel called Granicus valles, a tounge-shaped landslide in Terra Cimmeria, and a triple impact crater. The Mars Reconnaissance Orbiter mission released views of layered rocks at the summit of Olympus mons, a closeup on a field of secondary craters from a larger impact, the north polar layered deposits, defrosting sand dunes in the region surrounding the north polar cap, a beautiful image of layers within the walls of a crater in Mawrth vallis, a photo of the ejecta blanket of a large impact crater, and lava flows on the flank of Pavonis Mons. Nothing was released last week by the Mars Express mission.

At the Moon, Chang'e 1 and Kaguya are currently in orbit. Nothing new was released from either mission last week. At Venus, Venus Express is currently in orbit. Nothing was released last week from that mission either. MESSENGER is cruising toward its second encounter with Mercury on October 6. It is 144 million kilometers from Earth and 128 million kilometers from Mercury. I wrote last week about a map released with new names for craters revealed during MESSENGER's first flyby.

Out in space, New Horizons is 8.99 AU from Earth and 21.80 AU from Pluto, approaching Saturn's distance from the Sun. As of March 14 (the last date for which information is available), Voyager 1 and 2 were 105.72 and 85.36 AU from the Sun, and both were operating nominally. Dawn, Deep Impact, Hayabusa, Rosetta, and Stardust are all in cruise mode, talking to Earth from time to time; Genesis is in hibernation, awaiting an extended mission.