Looking for Martian life? Phoenix may find it

Analyzing water and soil
Phoenix has two prime directives.

First is to probe the history of liquid water that may have existed in that area as recently as 100,000 years ago. Scientists will analyze the chemistry and mineralogy of the soil and ice using the lander's instruments.

Furthermore, Phoenix will assess the habitability of the Martian polar environment by tasking sophisticated chemical experiments to assess the soil’s composition of life-giving elements such as carbon, nitrogen, phosphorus and hydrogen.

Phoenix will dig deep enough into the soil to analyze the soil environment, presumably protected from ultraviolet rays, and look for organic signatures and assess the potential habitability of the subsurface.

Ease on down
But setting the spacecraft down safely onto Mars is a bit of déjà vu all over again.

When Phoenix plows through Mars’ atmosphere in May 2008 and speeds toward the planet’s surface, its touchdown won’t rely on airbags and bouncing to a full stop — as has been the case for the last three successful NASA Mars landings.

Once free of a parachute, Phoenix will depend upon an "ease on down" propulsion system that was last utilized on the failed Mars Polar Lander mission.

Lockheed Martin Space Systems near Denver — the builder of both Phoenix and the lost Mars Polar Lander — has been busy performing shakeout tests of the rebuilt descent propulsion hardware.

For example, in a test stand, water jets have been attached where Phoenix thrusters are placed and then fired to mimic the kind of machine-gun pulsing and vibration the lander will undergo en route to a hoped-for soft touchdown.

Bellagio test run
Showing a film clip of a "water hammer" trial run, "some call it the Bellagio test," Smith noted. "If you turn it upside down, you’d have the fountains," likening it to the Bellagio luxury resort in Las Vegas and its majestic spouting water show.

During the descent to Mars, however, Phoenix's thrusters will gulp and heave out hydrazine.

The engine effluents striking the landing spot in which Phoenix will conduct science "is a matter of some concern to those members of the science team," Smith explained. While the most ultra-pure hydrazine is to be used, some uncombusted fuel will reach the surface.

"So we are very much worried about this issue," Smith said. "We are trying to find ways that we can work with the soil and try to avoid the contamination from the hydrazine and the exhaust gases."

Science on deck
Shortly after landing, Phoenix will unleash its two solar panels. They unfurl like Chinese fans. The tip-to-tip spread of the solar arrays covers nearly 12 feet (4 meters), with the lander sitting roughly 4 feet (1.2 meters) above the terrain.

The "deck" of the legged lander is 4 feet (1.2 meters) across — about the size of a breakfast table — and is loaded with science equipment.

Other critical instruments are also deployed right after the lander touches down. A camera system begins snapping images of the surrounding terrain and the area in which the robotic arm will be digging. Also, gear onboard starts to sample the weather at the landing site.

Presently, only a UHF antenna is on the lander, meaning all communications with the spacecraft are handled through Mars orbiters. An X band antenna was dropped, shaving off 33 pounds (15 kilograms) of weight and $10 million in cost to the project.

Sterilized ‘body bag’
A critical item on Phoenix is a nearly 8-foot-long (2.35-meter-long) robot arm. "It’s quite a strong arm," Smith noted, "but not strong enough to dig through solid ice." Like a backhoe, this appendage can use its sharp prongs and serrated blades to tear and scrape the soil.

In the first few weeks of the Phoenix mission, the arm is destined to dig very rapidly, "just to see if we can find quickly the depth to ice," Smith pointed out.

Samples successfully scooped up by the arm are placed into a Thermal and Evolved Gas Analyzer, or TEGA — a combination high-temperature furnace and mass spectrometer instrument that scientists will use to analyze Martian ice and soil samples. Specimens are also delivered to water chambers and a microscope station.

However, before the agile robot arm is put to work, it must first unsheathe itself from a sterilized "body bag" in which it is housed during the ride to Mars. That’s necessary as the arm itself will also be sterilized, precluding it from introducing tag-along microbes from Earth to the surface of Mars, Smith said.

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