From the Everett and Seattle Astronomical

040107.doc Spiritual Experience on Mars Page 1 of 5

From Celestial North, this is IT’S OVER YOUR HEAD for the week of

January 7th, 2004, a look at what’s up in the sky over Puget Sound.

The New Year brought together revelers the world over for jubilant parties and celebrations:

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But what you just heard was a somewhat belated New Year’s celebration that occurred on Saturday, January 3rd. And the revelers were members of the

Mars Exploration Rover “EDL” (ee-dee-EL) team, celebrating the arrival of Spirit,

the first of the Mars Exploration Rovers, as it made a picture-perfect landing on

the Red Planet.

“EDL” stands for “Entry, Descent, and Landing”, and the EDL team is responsible for that phase of the spacecraft’s journey in which it goes from

12,000 miles per hour to zero miles per hour in the span of about 6 minutes.

The rover itself spent the journey from Earth to Mars folded up like a pretzel and tucked inside a collapsed lander platform. The lander was enveloped in the deflated Kevlar airbags, which in turn were encased in a protective aeroshell. All of this was attached to a cruise stage, which provided solar power, communications antennas, and steering jets. About 15 minutes prior to entering the Martian atmosphere, Spirit jettisoned the cruise stage in preparation for its fiery ordeal.

During the first four minutes of its atmospheric plunge, the spacecraft decelerated from 12,000 mph to just under 1,000 mph. The bottom portion of the aeroshell protected its curled up cargo from the 2600-degree-Fahrenheit temperature generated by the friction of its passage.

Less than two minutes before touchdown, Spirit’s parachute deployed to further slow its velocity. About 20 seconds later, the lower half of the aeroshell was jettisoned, and the lander dropped from a tether connected to the upper half of the shell still attached to the parachute. Then, just six seconds prior to landing, the protective Kevlar airbags inflated, retro-rockets on the upper shell fired, and the tether was cut, releasing the lander about 50 feet from the ground.

The celebration you heard earlier in the broadcast was the EDL team’s response to confirmation that Spirit had survived its rough, bouncing landing and that its signal was being picked up by earth-based ground stations.

Within only a few hours of landing, the airbags were deflated, and Spirit returned its first black-and-white pictures of the Martian surface, sky, and even a couple of self-portraits. Then, on Tuesday, January 6th, NASA released the first high-resolution color images from Spirit. The resolution of these images are 3-4 times better than for any other images ever obtained of the surface of Mars, or any other planet for that matter.

Spirit ended up less than 6 miles from the center of its intended landing site, a bull’s-eye when one considers that it traveled more than 300 million miles from

Earth to Mars. Initial analysis of the surroundings shows that there are interesting rocks to study nearby, but not so many that they will make navigation difficult. A small circular depression, nicknamed “Sleepy Hollow”, about 20 yards due north of the lander, appears to be a good candidate for Spirit’s first excursion. It may be a dust-filled secondary impact crater, providing an opportunity to investigate rocks thrown up from below the surface.

Spirit now rests within a 100-mile wide crater named Gusev. While there are countless craters on Mars, this one is special, in that it appears to have once held an ancient lake. A riverbed, now long extinct, once emptied into Gusev crater through a breach in its southern rim. Sediments laid down as the water pooled in the crater would have preserved a record of the past aqueous environment there. But this sediment may be buried under subsequent layers, possibly from volcanic eruptions or wind-blown dust. However, there are many smaller, younger craters within the larger Gusev crater, and perhaps some of these impacts might have excavated those buried sedimentary layers up to the surface, which is why the Spirit team is so interested in the “Sleepy Hollow” depression.

Most of Spirit’s instruments have now been checked out and are in fine working order. The Spirit team is in the process of unfolding the rover, which will take several days. Then it will be time to leave the landing platform to begin exploring the surface and those intriguing Martian rocks.

The Spirit EDL team has set the bar very high for Mars landings. But the second MER EDL team will have a chance to best them, when Spirit’s twin rover,

Opportunity, arrives at the Red Planet on Saturday, January 24th.

On Saturday and Sunday, January 24th and 25th, you can find out the very

latest about Mars exploration. There will be three opportunities on both days to

join me, Greg Donohue, NASA/JPL Solar System Ambassador, for my

multimedia presentation, “Mars Attacked!” Each session will be followed by a

question and answer period. To find out more, go to the “Events Calendar”

section of the Celestial North website.

We’re on the web at CelestialNorth.org. Until next time, this is Greg

Donohue, with a reminder that the night is very large, and full of wonders!

REFERENCES:

http://marsrovers.jpl.nasa.gov/newsroom/merlandings.pdf

http://athena.cornell.edu/

http://marsrovers.jpl.nasa.gov/home/index.html