This month we bid a fond farewell to a scientific marvel.  Earlier this month on 2 November, the expected signals from the space robot Mars Global Surveyor were not received.  Despite repeated efforts, the MGS still has not called home.  So why should we care?

The Mars Global Surveyor was launched on 7 November 1996 at a time when the US was tentatively returning to the solar system.  The MGS launch followed the disastrous fate of the Mars Observer, which was sent aloft in 1992.  After an 11-month journey, that spacecraft was three days from entering Mars orbit when all contact was abruptly lost on 23 August 1993.  The loss of contact coincided with a pressurization sequence of a fuel tank that would have provided the braking energy to put the spacecraft into Martian orbit.  The fuel tank may have exploded, destroying the spacecraft.

No probes were launched for Mars in the 1994 window (Martian probes can only be economically launched every two years), but on 7 November 1996, the US launched the Mars Global Surveyor.  In line with the new streamlined NASA (which actually means do more with less money, a concept most of us are familiar with), planetary missions are no longer sent in pairs but the Mars Global Surveyor was the sister ship to the Mars Observer with a little bit of upgraded equipment.

The Mars Global Surveyor reached Mars in September 1997 but one of her solar panels failed to unfurl properly.  This was a problem for the mission as the solar panels were to be used for aerobraking, a technique that uses atmospheric drag to slow the spacecraft.  Scientists couldn’t aerobrake the spacecraft as originally intended because they feared the solar panel would snap off.  It took an entire year longer than expected, but the Mars Global Surveyor finally achieved its polar mapping orbit in March 1999. 

The solar panels apparently caused the spacecraft’s final demise.  Preliminary indications are that the functional solar panel became difficult to pivot.  Since the solar panels must always point toward the Sun to generate power, the spacecraft may not be able to generate enough power to communicate.

In the eight years that MGS has orbited Mars it has returned almost a quarter of a million pictures during the course of three complete Martian years (Mars years are roughly two Earth years long).  This has allowed us to see Mars as it changes through its seasons and also allowed us to determine that for three Martian summers in a row, deposits of carbon-dioxide ice near Mars' South Pole shrunk from the previous year's size, suggesting a climate change in progress.  Mars may be undergoing global warming like Earth, but they can’t blame humans for that!  (At least not yet!)

Seasonal changes on Mars imaged by the Mars Global Surveyor  NASA/JPL/MSSS/ASU

Thanks to MGS and her orbiting cohorts, we know more about the surfaceof Mars than we do about the surface of Earth (satellites can’t see the ocean bottom) and in addition to all those pictures, the Mars
Global Surveyor evaluated the landing sites for the twin NASA rovers Spirit and Opportunity and has allowed scientists to evaluate future landing sites for the Phoenix and Mars Science Laboratory missions.  It monitored atmospheric conditions while newer Mars orbiters like the Mars. Reconnaissance Orbiter were aerobraking, making those missions much safer and it has served as a relay link for the rovers and taken their pictures thereby providing mapping information about their surroundings.
Wheel tracks left by NASA's Mars Exploration Rover Spirit, and even the rover itself, are visible in this image from NASA's Mars Global Surveyor orbiter.  NASA/JPL/MSSS

	The other missions have returned the favor.  The Mars Reconnaissance Orbiter has been searching for MGS in an attempt to take its picture.  Although the MRO hasn’t found the Global Surveyor yet, these two pictures show that it’s possible.  The first image is a picture that the Mars Global Surveyor took of the Mars Reconnaissance orbiter shortly after the MRO achieved orbit last year.

As mentioned, the Mars Global Surveyor has also served as a message relay station for the two rovers Spirit and Opportunity that are still roving on Mars.  Last week, Opportunity tried to contact its old friend and failed.

I’ve run out of space to tell you about more of the astounding discoveries by this amazing robot so I’ll close with a quote by Tom Thorpe, the project manager for the Mars Global Surveyor at JPL.

"It is an extraordinary machine that has done things the designers never envisioned despite a broken wing, a failed gyro and a worn-out reaction wheel.  The builders and operating staff can be proud of their legacy of scientific discoveries and key support for subsequent missions."

Amen, Mr. Thorpe.  Amen.

Cruise on over to the Deep Website at www.thedeepradioshow.com to learn more about Mars and many other topics.  Enjoy!

To commemorate its decade in space and over 240,000 images returned, the Mars Orbiter Camera on Mars Global Surveyor offers a stunning image of clouds swirling elegantly above the Martian north pole.