Source: http://www.nytimes.com/2007/07/31/science/space/31phoe.html?_r=1&ref=science&oref=slogin
By WARREN E. LEARY
Published: July 31, 2007
WASHINGTON, July 30 — NASA is about to launch a scientific laboratory to Mars that will be the first spacecraft to land in the northern polar region of the planet and dig for evidence of water or other conditions that could support some form of life.
The spacecraft, Mars Phoenix Lander, is set to launch from Cape Canaveral, Fla., on a Delta II rocket during a three-week window that opens Friday. If the 770-pound lander touches down safely after its 10-month journey, it will spend three months or longer probing the ground and monitoring the weather above.
Unlike rover missions that explore large areas, Phoenix is to stay on one spot in the permafrost region of the Martian arctic and use a mechanical arm to explore the area in detail. “This is a vertical mission,” said Peter H. Smith of the University of Arizona, the mission’s principal scientist. “We are going to dig down and not explore horizontally.”
The target area rests at latitudes equivalent on Earth to Northern Alaska, Siberia or Greenland, Mr. Smith said. It is covered with polar ice in the winter, but Phoenix is to arrive in the summer when the ground is mostly clear.
After landing, the robot spacecraft will unfurl a pair of circular solar power arrays that give it a width of 18 feet. It will deploy a pair of stereoscopic color cameras on a mast that extends 7 feet above the surface to record panoramic views, and extend a 4-foot mast bearing temperature sensors from an onboard weather station supplied by the Canadian Space Agency.
The weather station, designed to operate even after the craft’s primary digging mission is completed, is to track daily and seasonal changes in temperature, atmospheric pressure and wind speed and direction. In addition, a pulsing laser will fire into the atmosphere to measure the size and altitude of dust and ice particles in the vicinity.
With a 7.7-foot-long hinged arm that operates like a backhoe, the craft is to dig a series of trenches more than 20 inches into the ground with a movable metal scoop that has sharp prongs and serrated blades on the end. At full range, the arm can reach eight square yards of surface area near the lander, Mr. Smith said.
Guided by a camera on the end of the scoop, scientists will select soil and ice samples for detailed study by instruments on the lander. For one experiment, the Thermal and Evolved Gas Analyzer, samples will be dropped into a hopper to feed eight single-use ovens the size of an ink cartridge in a ballpoint pen. The sample will be slowly heated to 1,800 degrees Fahrenheit to study the transition from solid to liquid to gas, and the vapors analyzed by a mass spectrometer to measure the mass and composition of specific molecules.
Four other samples are to be examined in a miniature wet chemistry laboratory, where they will be stirred into a prewarmed solution and mixed with chemicals to tease out certain constituents, such as carbonates, sulfates and soil oxidants. Such components could either encourage or deter the formation of life if liquid water were available at times, scientists said.
This laboratory also contains two microscopes to examine the fine structure of soil and ice samples, revealing features as small as 1/1,000th the width of a human hair that could be evidence of past liquid water on the planet.
Phoenix draws its name from the mythical bird that rose from its ashes because it is made of parts of two earlier efforts to explore Mars. “It’s really getting a second chance, as its name implies,” said Douglas McCuistion, director of the Mars Exploration Program at NASA. “It is mainly refurbished hardware.”
The spacecraft is made of the supporting structure and some instruments from the 2001 Mars Surveyor lander, which never flew because of cost overruns, and several backup instruments from the unsuccessful Mars Polar Lander in 1999.
Mr. McCuistion estimated the project would cost $420 million, including $90 million for the launch rocket. He said the amount was $25 million to $30 million above initial estimates because the program decided to do more tests and simulations to help assure mission success.
Recent spacecraft like the rovers Spirit and Opportunity have landed on Mars encased in airbags to cushion their fall and bounce around obstacles. Phoenix Lander is too heavy for the airbag approach so it will make a fiery entry into Mars’s atmosphere protected by a heat shield before being slowed by a parachute and eventually making a soft landing with the help of pulsing retro rockets.
Mr. McCuistion noted that the success rate for landing spacecraft on Mars was under 50 percent, and that there was added risk in attempting a soft landing.
While Phoenix is to operate during the Martian summer, scientists hope the spacecraft survives dwindling sunlight and power to see approaching winter cover the area with ice. “I’d be thrilled if we could last long enough to see ice form around the spacecraft,” Mr. Smith said.
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NASA/JPL/UA/Lockheed Martin.
BIG DIG A technician assembling the Mars Phoenix Lander last year in Denver.
Fausto Intilla's web site: www.oloscience.com
Sat Aug 04, 2007 10:48 pm