Rarin’ to go

Phoenix prepares to scoop up the soil

After a day’s delay, the robotic arm on Mars Phoenix Lander is free of its shackles. “Our arm was cooped up in restraints for 14 months and is rarin’ to go,” Matt Robinson of NASA’s Jet Propulsion Laboratory in Pasadena, Calif., said during a May 28 press briefing at the University of Arizona in Tucson.

FISH-EYE VIEW In this fish-eye view of Phoenix and the horizon, north is up. West shows the robotic arm’s scoop. The view slightly west of due south shows Phoenix’s mast with temperature sensors. The hummocky terrain with troughs in this image of Mars is typical of Earth’s polar region, where permafrost is at the surface and ice just below. JPL/NASA, U. of Arizona

LAY OF THE LAND This view of the Phoenix landing site shows the lengths, in inches, of an assortment of flat rocks.Click on the image for a larger view. JPL/NASA, U. of Arizona

Earlier today, scientists relayed commands to fully deploy the arm and begin other tests in preparation for the first dig into Martian soil, scheduled to begin next week.

Scientists want to study how each of the arm’s four joints performs at the warmest (up to -80 degrees C) and coldest (-30 degrees C) temperatures possible at Phoenix’s landing site in the north polar region. Before telling the lander to dig, researchers also need to finish checking the stability of Phoenix’s three legs, or footpads.

The arm’s first assignment will be to use its camera to look under the craft and make sure Phoenix isn’t sitting on top of a large rock.

Once the arm scoops samples, it will deliver them to miniature ovens, which will determine the composition of both topsoil and the ice believed to lie just a few centimeters below the surface at the landing site. Phoenix touched down on May 25 after a 675-million–kilometer journey from Earth.

The craft completed and relayed to Earth its first 360-degree, low-resolution view of the landing site, which shows hummocks, troughs and an assortment of flat, fist-size rocks. The rocks are small enough for the robotic arm to push them aside if needed, said Phoenix principal investigator Peter Smith of the University of Arizona in Tucson.

Phoenix also began using its laser instrument, beaming pulses of green laser light into the atmosphere to detect dust and clouds up to 20 kilometers in altitude.

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