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Phoenix diary: Mission to Mars
2008-06-17 08:54:43



The Nation Press -

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.

Soil on microscope (Nasa)
The scoop delivered soil to the lander's microscope

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.

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.

Martian soil (Nasa)
White material at the bottom of the trench could be ice

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.

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.

Phoenix scoop (Nasa)
Perserverance finally paid off for the Phoenix team

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.

Microscopy image (Nasa)
Phoenix has returned its first microscope images
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.

Grand site

It's a truism that no camera can capture the vast scale of the Grand Canyon. But as we amble along the canyon's North Rim, it is the timescale as much as the immensity of what we are gazing at that is staggering.

Grand Canyon (Tom Pike)
The Grand Canyon was created in about 20 million years
It took 20 million years for the Colorado River to carve out the scene in front of us.

But even that is an instant compared to the four billion years that Mars has had to grind its own surface down to a fine dust.

We believe Mars was a wetter and warmer place early in its history.

But it dried out long ago, and since then, the dust has been whipped into innumerable sandstorms - often enveloping the entire planet.

It is these tortured individual particles that we hope to see for the first time.

First images

I'm back in the science operations center (SOC) in Tucson just in time for the data to arrive back on Earth. This time, the transmission stutters and we wait impatiently for the full pictures to come down.

No one has looked at the dust of Mars at this resolution before, and now I gasp as the images appear and we see the sheer variety of what we have collected.

From tiny particles of the palest white to black rounded beads, we're the first to see what coats Mars and makes the skies pink.

Zooming in, we see finer and finer particles, right to the smallest grains that our optical microscope can make out. We have run out of resolution and that is why we have our atomic force microscope to look even more closely at the dust.

Team member Urs Staufer is impatient, but it will be a week or more before we can move in his instrument and try to image the very smallest of the particles.

The next morning, I drive down from the microscopy house to present our first microscope images at the daily Phoenix press conference. I'm no longer a tourist on Mars, but a scientist. And as a scientist, this is about as good as it gets.

 

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.

The microscope station photographed on Earth (Pike)
The microscope is a key instrument on the Phoenix lander
Today we have our first chance to get images from the optical microscope of the Phoenix lander as it stands on the northern Martian plains.

Yesterday, we had commanded the sample wheel to bring our test substrates under the gaze of the optical microscope, ordered the LEDs to turn on and illuminate the scene, and asked the microscope to take a series of images.

If it all worked, these would be the highest resolution pictures taken from another planet. Today, the data is making its way back to Earth, first transmitted up to Nasa's Odyssey orbiter circling Mars.

Then, as Earth comes into view, Odyssey relays the data packets to the massive parabolic receivers of the Deep Space Network which then give the packets a final push to where the mission scientists are waiting at the science operations center, the SOC, in Tucson.

We gather round Sanjay's laptop in the downlink room, nervously chatting about all that could go wrong.

Wait and see

During testing for the mission, the images had often come out fuzzy - we found it very difficult to keep precise enough control of the sample wheel.

The microscope station photographed on Mars (Pike)
Meca is now working on the surface of the Red Planet
What should have been crisp pictures had become out-of-focus blurs. Sanjay and Hanna had spent long days on the copy of the microscope station at Imperial, working out the intricacies of how to drive the sample wheel precisely. Meanwhile, the Phoenix microscope itself had been cruising towards Mars.

We are about to find out if they learnt how to drive it.

Data is now flowing back and we immediately see that the spacecraft has sent back all of the pictures we had asked it to take.

Sanjay has prepared computer code that will eagerly pull apart the data packets, reconstruct the pictures, and immediately throw the microscope images up on his screen.

Eleven years shrinks down to the one second it takes to see our images cascade on to the laptop. They're as crisp as any we've seen.

The first image is a test. In truth, there's really not that much to look at - a series of white rectangles covering 1mm by 2mm, with two blurred shadows like a couple of fence posts in one corner.

These shadows are the first two beams of the atomic force microscope. With this second microscope we hope to zoom in even further.

The silicon beams are thinner than the thinnest tissue paper, but have survived the trip intact. Urs Staufer, who put together the atomic force microscope, is very happy.

As we look closely, we see the network of fine scratches left in polishing the test substrate. The light from the LEDs, bouncing off the substrate and through the optics of the microscope to its camera, is providing the finest detail ever seen on another planet.

The sun is just hitting the Tucson mountains as we emerge from the SOC and head back to the microscope house.

But we're working Mars shifts and it's dinner time for us. We start up the barbecue under the first light of the Arizonan dawn.

It's certainly worth a toast - we're now ready to take the closest look ever at the dust and soil or even ice that Phoenix digs up from below the surface of Mars.

 

POSTCARD FROM MARS

The feeling is almost overwhelming as we listen to the live commentary from Nasa's Jet Propulsion Laboratory (JPL) in California as Phoenix descends towards the surface of Mars.

Microscopy team (Tom Pike)
There were big smiles as the team realised the mission was "go"

The radar gives us the height: first we're closing hundreds of metres at a time - surely this is too fast.

But in the last tens of metres the retro-rockets kick in. We slow to a crawl, and Phoenix is given the graceful landing that JPL promised.

The science operations center (SOC) raises a huge cheer that must echo across Tucson. We embrace our colleagues, some of whom we've worked with for over ten years while putting this mission together.

Then I hug my wife and kids - they'll be seeing a lot less of me for the next three months.

Critical information

The first minute after landing Phoenix tells us all it can before concentrating on fanning out its solar arrays.

Scientists in science operations center, Tucson (Tom Pike)
The first pictures from Mars were studied closely by the scientists

One critical piece of information - we're tilted by a mere one quarter of a degree. Even before we see any images, we know we have landed on the flattest of plains.

There's now a two-hour wait until the first of these images can be sent back to Earth. Time to share a last meal with our families before we walk over to the secure area of the SOC where we will get started with mission operations.

We've trained so often it first feels like another mission simulation, although we now all have broad smiles on our faces.

As the images start coming in, we all feel the focus of the world's gaze slide from Pasadena, where JPL controlled the landing, to where we're standing in Tucson.

First comes the news we have one of the necessary ingredients for a successful mission - we see the solar arrays are deployed and hear that the batteries are fully charged.

Then we get a picture of one footpad showing a light covering of material kicked up by the retro-rockets. Any fine particles lofted during the landing will provide the first sample to look at with the microscopes on Phoenix.

The room gasps and cheers as Phoenix sends back the panoramic images. The cameras are working superbly - we get more images back than we'd ever managed during operations training.

As the small tilt indicated told us, we've landed on a very flat plain. But the landscape is far from featureless.

We see the surface cracked into polygons, a sign of the forces created by the ice we believe is just below the surface. It will be difficult to control the urge to ask Phoenix to dig down as quickly as possible.

But Phoenix has exceeded our expectations and doesn't deserve to be rushed. So far, it has been the perfect traveller, sending us back a postcard on the day that it arrives.

 

WAITING FOR PHOENIX

Phoenix lands today. The Imperial team is now in the US and we're settling in to the Phoenix "microscopy house", our home in Tucson, Arizona, for the three months of the mission.

Scientist attaches foil to windows (Tom Pike)
Foil on the windows helps protect against "Mars lag"
In our case, settling in involves a little more than unpacking our suitcases - we're also taping aluminium foil on the inside of all the bedroom windows.

The neighbours must be feeling rather worried about us, but there's a good reason for what looks like the first signs of collective madness.

We're going to be working on a shift system locked on Mars, not Earth, time. As Mars has a twenty-four-and-a-half hour day we'll be drifting in and out of synchronicity with our neighbours and, half the time, sleeping through the day.

We have experts from Harvard University helping us to overcome "Mars lag" - the continuous battle between our body clocks and a mission schedule working to Mars time.

Some of the tools were developed during the missions of the two rovers still trundling round Mars. The foil will black out our rooms, helping promote melanin production when we need to sleep.

As well as potentially helping us to sleep better, installing the aluminium foil keeps us busy and gives us less time to worry - it's difficult not to mentally replay what Nasa calls the "six minutes of terror" Phoenix will have to endure to get down to the surface of Mars.

But we can't long keep away from the heart of Phoenix activity on Earth - the science operations center, affectionately known as the SOC. Hanna and I take the fifteen-minute drive from the microscopy house to where the mission will unfold after Phoenix lands. But it's now eerily quiet in the SOC.

Empty tables are arrayed in front of a huge screen round around which we will be gathering tomorrow. We'll be anxiously awaiting the first message at 1653 (local time) from Phoenix, telling us it has made it down to the surface in one piece.

Science operations center (Tom Pike)
A huge screen has been set up in the science operations center
To the side, an Earth-bound version of the lander, which we use for testing, stands quietly in a "stage set" of Mars while its brother is fast closing the last million miles to the planet's surface.

There is a one-minute window directly after landing for Phoenix to send its safe-arrival message. The lander will then concentrate on getting its power sources operational. Two fan-like solar panels will unfurl to capture the weak sunshine of the Martian "Arctic".

In the meantime, the orbiters already circling Mars will send back their accounts of the landing, including the running commentary sent by Phoenix to the spacecraft during its descent.

By then, we should know Phoenix's fate, with a second chance for confirmation about an hour after landing. The two previous failed missions to Mars - the 1998 Mars Polar Lander and Beagle 2 in 2004 - took weeks before issuing their death certificates. If the worst happens to Phoenix, we'll know for sure the same day.

Tonight, the Phoenix microscope team will be sharing a last supper before landing. It's perfect weather for a barbecue round the pool at the microscopy house.

Fire and water - just the right ingredients for a final meal before Phoenix reaches Mars.

 

 

A GRACEFUL LANDING?

For the last nine-and-a half-months, the Phoenix spacecraft has been looping around the Sun, closing the distance between Earth and Mars.

While the spacecraft's tasks have been few - checking out and preparing the instruments, and producing very slight adjustments to its course - we have been working hard in London preparing for the 90-day mission.

Extreme Mars challenge: Entry, descent and landing

Using a copy of the microscope station on its way to Mars, the Imperial team - Sanjay Vijendran and Hanna Sykulska and myself - have been testing out the operations in the lab. Our aim has been to get to know the instrument (the Microscopy, Electrochemistry, and Conductivity Analyzer - or Meca) inside out before landing.

On Friday, we packed up our microscope to send to the Science Operations Center in Tucson, Arizona. Its job there will be to help us understand the behaviour of its twin on the surface of Mars.

Now, we can do little more before Phoenix reaches Mars except worry. Before launch last August, my kids scrawled "Go Phoenix!" on the beach at Cape Canaveral, and we enjoyed a perfect pre-dawn launch as the Delta II rocket carrying Phoenix arced over the Atlantic.

It is almost time for them to scribe a new command in the desert sands of Arizona: "Stop Phoenix!"

Big day

In a few day's time, early on Monday morning, Phoenix will take just seven minutes to screech to a halt on the icy northern plains of Mars.

It will all be over, one way or another, before the first signal even reaches Earth. No human intervention can overrule the landing sequence on the spacecraft computer that will set in motion first atmospheric entry, then a parachute descent and finally a thruster-controlled landing.

"Go Phoenix" written on the beach at Cape Canaveral, Florida (Tom Pike)
There are high hopes for Phoenix following its launch last year

While this sequence unfolds, we'll be waiting in the Science Operations Center for the signals to come back from Phoenix. Our colleagues and family will be there, including the "Meca babies" born to our instrument team in the years it has taken to prepare for the mission.

Their names, together with those of our colleagues who did not live to see Phoenix launch, form part of an eyetest chart for the microscope that is now hurtling towards Mars at 21,000km/h (13,000mph).

Phoenix will have a welcoming party - three orbiters already at Mars have been re-orientated to communicate with Phoenix before plasma blackout temporarily halts radio transmissions.

One of these, the Mars Express orbiter, will play paparazzo and attempt to snap Phoenix streaking through the atmosphere below on its way in to Mars.

Tense wait

As Phoenix slows down, communication will be re-established and a parachute deployed. As Mars only has 1% of the Earth's atmosphere this parachute doesn't create enough drag to slow us down enough for a soft landing, and so thrusters give us the final braking to ensure we touch down at a mere 8km/h (5mph).

Memorial plaque to Meca collaborators (Tom Pike)
Meca carries an "eyetest chart" with dedications to friends and family
In contrast to the bouncing airbag approach used in the last three missions, this is what the mission's principal investigator, Peter Smith, calls "landing gracefully".

The first sample for our microscope will be collected during the descent - a mixture of atmospheric dust and material kicked up by our landing. But it will be a few days before we get a chance to image this material.

In the meantime, the first images we should be seeing will be of the Phoenix lander and its immediate surroundings.

These photos might not be of huge scientific interest but we'll all be feeling like proud parents in Tucson as we share these first pictures with the rest of the world.

Or we could all be standing dumbstruck as the images fail to appear and we realise the mission most of us have spent over a decade preparing for lies as one more piece of space junk on the cruel surface of Mars.

Source : bbc
 
 
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