The Phoenix lander is studying its third sample of Martian soil in an onboard oven. The results may confirm the presence of a chemical called perchlorate, which could shed light on the history of water on the Red Planet.

In recent days, the lander has also dug its deepest trench yet in the soil, reaching a depth of about 9 centimetres.

On Saturday, a soil sample from near the surface of a trench called "Rosy Red" was dropped into an oven on an instrument called TEGA (Thermal and Evolved Gas Analyzer), which heats samples and measures gases released by volatile compounds.

Researchers will search the sample for signs of perchlorate, a chemical that can be carried away by liquid water and could thus reveal hints about how water may have flowed in the region in the past.

Attempts to detect perchlorate using TEGA in two other soil samples, from different areas, were inconclusive. One released oxygen – a component of perchlorate. But both it and a second soil sample failed to produce chlorine gas, another expected by-product.

But two other soil samples taken from this Rosy Red trench and a nearby trench called Snow White showed preliminary evidence of perchlorate when analysed in the lander''s MECA (Microscopy, Electrochemistry and Conductivity Analyzer) instrument.

Mechanical glitch

Delivering the latest soil sample to TEGA was not easy. On Thursday, Phoenix's robotic arm dumped the sample on top of TEGA's oven number 5. At first, only a few particles made it into the instrument's cylindrical compartment.