Google Earth Community: Phoenix on Mars - latest pictures

Nasa's Phoenix lander has provided the most magnified view ever of Martian soil.

Two scientific instruments, a microscope and a "bake-and-sniff" analyser, have begun inspecting soil samples delivered by the scoop on the spacecraft's robotic arm.

Dr Tom Pike, from Imperial College London, is one of the scientists working on the mission. He has been writing a diary for the BBC News website of his experiences.

MARTIAN LABOURS
It's been more than 30 years since a spacecraft has grabbed hold of the soil of Mars. In 1976, the two Viking landers sampled the surface for signs of life.

Since then there have been just three rovers on Mars, two of them still trundling around.

For them, the soil has been a road surface at best, a sand trap at worst. It has not been a substance to pick up and handle.

Phoenix has a much more sensual relationship with the planet's surface. It is digging furrows with its robot arm, stopping to collect a scoopful to bring back to the instruments waiting impatiently on its deck.

FIRST LIGHT
It was more than eleven years that Mike Hecht, from Nasa's Jet Propulsion Laboratory (JPL), and I first started thinking about sending a microscope to Mars.

White material at the bottom of the trench could be ice

But we have little idea what the soil is like, and we've been fumbling while we try to understand what we're handling. There's very little to help us get a feel of the soil.

The three orbiters circling Mars have sent back pictures at a level of detail never seen before of the surface of the planet.

We've looked down on ice-filled craters, canyons that dwarf even the largest on Earth, and glimpsed Phoenix itself swinging down on its parachute.

That last image now forms the backdrop to nearly every laptop screen at the science operations center (SOC). But the orbiters can only give the most tenuous clues as to how the soil might really feel.

Unpredictable soil

We suspect that, unlike the Earth, the make-up of the soil on Mars varies little - the planet is wreathed in the particles of innumerable global duststorms. That dust, though, has settled in very different environments.

At the poles it lands on ice caps, soon to be buried every Martian winter by ice fall. At the equator it becomes part of a dry desert.

Where Phoenix has landed, it seems to have a complicated relationship with the ice we think we've spotted just below the surface.

Our soil is unpredictable. First we dig up clumps that disintegrate overnight in the scoop. Then the robot arm tries to dump the first sample into the oven where it will be baked and analysed by a mass spectrometer, an instrument called TEGA.

Phoenix has returned its first microscope images

But the generous serving sits obstinately on the sieve that should just prevent pebbles jamming up the works. Even shaking the sieve has no effect. The TEGA team is becoming exasperated by the soil.

We're next with a delivery to the microscope and decide on a more delicate approach - sprinkling the soil on to our substrates.

The scoop has a vibrator built into it, designed to free up the hard ice and frozen soil we might collect later. During testing back in March, we worked alongside the robot-arm team using the copy of the spacecraft in Tucson. We found out how to use the vibrator to dust our substrates with material from a tilted scoop.

We want just enough soil to coat our substrates, but not so much that we can't make out the individual particles. But in our test in Tucson we could only use our best guess for the soil on Mars.

It has now taken three days of testing on Mars, sprinkling soil on the top of the black box housing the microscope, before we've convinced ourselves that we can deliver actual Martian soil.

We command the final sprinkle, followed by moving our sample wheel holding the substrates inside the box and round to the field of view of the microscope.

We hope this final movement, rotating the substrates from horizontal to vertical, will leave just the right amount of soil to peer at with the microscope.

At three the next morning we're back in the SOC, waiting again for our images to return from the spacecraft. We're much more confident that the microscope station will perform as commanded.

My doubt now is whether the Martian soil will cooperate. All eyes are on us - the mission will only proceed if we can be certain the microscope got the first sample of Martian soil.

Until we give the signal, the robot arm hangs frozen over the microscope enclosure.

The first images show the scoop and our substrates poking out of our box - with what looks like just the dusting we were looking for.

But it is not until Sanjay again decodes the incoming data that we see our first microscope images. The soil is scattered perfectly across the substrates. It's a Go.

Our excitement is mirrored by the TEGA team - on the seventh attempt at shaking their load, the obstinate soil has finally collapsed into their awaiting oven.

We congratulate each other like proud new parents - after a few anxious days of labour we've both got our deliveries from the surface of Mars.

THE DUST ON MARS
The first sample we want to look at with the microscope is an insurance policy. Even if the robot arm is for some reason unable to reach down and scratch out a sample for us, we know the lander's retro-rockets (fired at the Martian surface to slow the craft's descent on landing) would have done the trick.

We landed in a cloud of dust as Phoenix lowered itself onto the surface of Mars. We just had to be able to collect some of it.

So a month before landing, while still millions of kilometres away from Mars, we moved our first set of test substrates out of the microscope station enclosure ready to catch the debris thrown up during landing.

These substrates are the discs we use to hold the dust and soil of Mars in front of our microscopes.

We then wrote the spacecraft computer sequence to rotate the substrates back into the enclosure, focus the microscope and take the red, green and blue images to give us the colour pictures of the dust we have managed to collect.

All is set, and there's little else to do now but wait for the sequence to run. We bundle the kids into the car and take advantage of a couple of days off to head up to the Grand Canyon.

The news of Phoenix precedes us as we stay overnight on the way in Flagstaff. As we eat a late supper we're congratulated by our fellow diners on a mission that Arizonans have obviously taken to their hearts.

But until we have received our first images of dust, I still feel like a tourist rather than a scientist on Mars.

Source: BBC

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