Even on Mars, size counts.
NASA's Opportunity rover at Meridiani Planum has wheeled up to "Erebus Crater" - a sizable feature about 984 feet (300 meters) across.
The decision has been made by scientists and engineers operating the robot to go west, counterclockwise around the crater. Erebus is nearly twice the diameter of Endurance Crater, an earlier "pit stop" of Opportunity that produced a bonanza of science data.
"We're there, for all intents and purposes," said Steve Squyres of Cornell University in Ithaca, New York. Squyres is principal investigator for the Opportunity and Spirit Mars rover science instruments.
"We can see most of the crater from where we are right now, and we've made the decision that we're going to traverse around it on its western side," Squyres told SPACE.com. "We're actually going to start the drive around the crater by going north a little bit...to get onto terrain that's mostly bedrock...before we swing west."
Squyres said that as Opportunity makes its way counterclockwise around the crater, the science team and rover drivers are keeping their eyes sharp, looking for a safe place to possibly enter Erebus Crater.
"The goal being to get to a place we've named the 'Mogollon Rim'...on the western side. If we can find a safe place to go in, that's great... if we can't, we'll just continue on to the south," Squyres added.
On the other side of Mars--within Gusev Crater--the Spirit robot has been intently surveying the summit of Husband Hill.
Session work has included studying "Cliffhanger"--a windblown drift. Stereo imaging of "Tennessee Valley" from the summit is also on the action item list.
Increased attention is being paid on how best to get down from the summit, Squyres noted in an update on the Cornell University-based Mars Exploration Rover website. Which way to go and what route should be picked are under discussion, he reported.
"The hill is very steep in places....and the orbital images show a lot of tasty geology, some of it in pretty nasty-looking places. All in all, the next several weeks are going to present us with some of the most interesting route-finding decisions that we've faced in a long time, on both sides of the planet," Squyres noted.
Meteor search campaign
Spirit has also turned nighttime sky-watcher. The Mars machinery is engaged in "shooting sessions"--not only imaging the two moons of the red planet, Phobos and Deimos, but will also be on the lookout for shooting stars.
"We're almost done with our Phobos and Deimos astrometric and color imaging," said Jim Bell, an Associate Professor in the Cornell University Astronomy Department. Bell is lead scientist for the Panoramic Camera color imaging system carried by both Spirit and Opportunity.
"We have a few more sequences to run...and we'll also be trying to image Phobos going into and out of the Mars shadow in a 'lunar' eclipse later in October for additional orbit timing data," Bell explained.
"Next we are going to start our meteor search campaign in earnest," Bell told SPACE.com. "We have to finish up our nighttime observation campaigns relatively soon. That's because we're at the peak of our power availability now on Spirit over the coming months, as the Sun starts to get lower and Mars gets farther from the Sun."
Bell said rover engineers for Spirit may not be able to muster enough power to operate the cameras at night. "So the clock is ticking," he added.
Back on the other side of Mars, nighttime observations of the martian sky by Opportunity for a longer period of time may be possible, Bell said, because that rover is closer to the equator. However, Opportunity is also dealing with a power-draining heater unit. It is stuck in the on position. Too early to tell if that situation may deter the robot's nighttime sky scanning, he said.