Nerves Run High for Spacecraft's Sunday Mars Landing

This story was updated at 5:46 p.m. EDT.

PASADENA, Calif. – Excitement and nerves are both running high among NASA scientists as they prepare for the Phoenix Mars Lander?s planned Sunday arrival at the red planet, mission scientists said today.

The spacecraft is still in good shape and on track as it nears the finish line of its 422 million-mile (679 million km) trek to the Martian arctic.

?Well this is exciting, a very exciting day,? said Doug McCuistion, director of the Mars Exploration program for NASA, at a press briefing at here at the agency?s Jet Propulsion Laboratory (JPL). ?The atmosphere here at JPL is electric.?

But in addition to excitement, Phoenix scientists are getting a strong case of nerves.

?The anxiety level is getting high,? said Phoenix project manager at JPL Barry Goldstein.

?I?m getting a real case of the heebie-jeebies now,? echoed Joe Guinn, Phoenix mission manager at JPL.

The craft, now just over 1 million miles (about 1.6 million km) from Mars, is slated to land in the north polar regions of Mars in the Vastitas Borealis plains. Mission scientists expect to receive the signal that Phoenix has landed on Sunday at 7:53 p.m. EDT (2353 GMT). The first images from the craft could be sent back to Earth as soon as a couple of hours after landing.

The $420-million mission, which launched last August, plans to dig down to the rock-hard layers of water ice thought to lie under the Martian soil near the planet?s north pole. It is designed to test the soil and ice for signs that liquid water existed there in the past using some of the instruments originally created for its ill-fated predecessor, the Mars Polar Lander, which failed before landing in 1999.

A trajectory correction maneuver opportunity scheduled for late this evening could be skipped, mission engineers said, as Phoenix still seems to be flying true after its last thruster maneuver a week ago. The craft has already skipped one correction opportunity. The team will have one more opportunity to adjust Phoenix?s trajectory tomorrow morning if required.

The likelihood of needing to make a correction tomorrow will influence the decision to make a correction today, Goldstein told SPACE.com. Making a maneuver today, while the landing is still almost 24 hours away, is much less nerve-wracking than making one tomorrow because there?s more time to see if the maneuver worked, he said. Having to make a maneuver just eight hours before landing leaves much less wiggle room.

?That?s really scary,? Goldstein said.

Goldstein says the series of meetings and the work to prepare for the landing tomorrow help take his mind off of his nerves, that and eating lots of ice cream.

He also said that a long-standing tradition at JPL to kill the butterflies on landing day is to pass out peanuts to all the people in mission control. The tradition supposedly goes back to the Ranger missions to the moon; after the first few failed, people began to eat peanuts to calm their nerves.

?I already have the peanuts purchased,? Goldstein said.

The weather on Mars also still looks optimal for landing day. Only one dust storm has been spotted in the area, and was actually seen directly over the landing site yesterday, but it will likely be out of the way come landing time given its current rate of movement, Goldstein told reporters on a tour of JPL mission control yesterday.

?The good news is? that cloud has now passed over our landing site,? said Phoenix principal investigator Peter Smith of the University of Arizona, adding that mission scientists are ?watching the weather, we?re going to be watching it throughout the mission.?

What has scientists most on edge is Phoenix?s ?fiery entrance into the atmosphere? tomorrow, as Goldstein put it. While each of the individual systems that have to deploy tomorrow, from the parachute, to releasing the back shield and firing the thrusters, have checked out so far, it?s the strict sequence that the systems have to follow that make mission scientists most nervous.

The last successful landings on Mars were the two Mars Exploration Rovers, Spirit and Opportunity in January 2004, with the hardy robots still exploring the planet today.

Phoenix won?t use the same airbag-cushioned landing technique that brought those crafts safely to the Martian surface. Instead, it will use thrusters to slow its rapid descent through the atmosphere. This technique has not been used successfully since the Viking mission in the 1970s and was last used by the failed Mars Polar Lander (MPL) in 1999.

The mission team has corrected many of the problems encountered with MPL, but as McCuistion said during the briefing, ?Mars is always there to throw those unknowns at us.?

NASA's next Phoenix mission briefing will be broadcast live on NASA TV at 3:00 p.m. EDT (1900 GMT) on Sunday, May 25. Click here for SPACE.com's Phoenix mission coverage and a link to NASA TV.

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