The US space agency (Nasa) is to begin taking steps to spring its robotic rover Opportunity from the sand trap it is stranded in on Mars.
Engineers simulated the conditions faced by the rover
Engineers have tried simulating the conditions facing the rover on the Red Planet, to determine how best to extricate the robot from its jam.
Opportunity has been bogged down in a sand dune since a drive on 26 April.
After an external review, Nasa could begin developing the first commands to send to the rover on Monday.
Opportunity is positioned across the ridge of an elongated dune or ripple of soft sand that is about one-third of a metre (one foot) tall and 2.5m (8ft) wide.
"We've climbed over dozens of ripples, but this one is different in that it seems to be a little taller and to have a steeper slope, about 15 degrees on part of its face," said rover engineer Mark Maimone.
The mission team has tried driving a test rover through manmade dunes at the Jet Propulsion Laboratory's testing facility in Pasadena, California.
The rover had no problem driving away, even when sunk belly-deep. But the test used the sand already available, which is thought to offer more traction than the finer, looser material at Opportunity's current position on Mars.
So researchers made up two tonnes of soil like that around Opportunity's wheels from play sand, diatomaceous Earth for swimming pool filters and mortar clay powder.
Experiments in this more powdery material suggest that Opportunity can drive out of the dune after some initial wheel-spinning.
Since landing more than 15 months ago, Opportunity has driven 5.4km (3.3 miles) across the surface of the Red Planet.