Facing a deadline imposed by nature itself, NASA is said to be hearing the message from the planetary science community that due to no other reason that circumstance a mission to Pluto must launch in 2004 to reach the distant world by 2012 before its atmosphere freezes out as the planet moves far from the Sun on its highly elliptic 248-year orbit.

As reported last month in our series on the recent meeting of NASA's Solar System Exploration Subcommittee, the Pluto mission had encountered a double whammy.

Not only had it - and the other outer planet mission - Europa Orbiter encountered major cost rises due to technical problems, but in late October NASA at the direction of Administrator Dan Goldin transferred $100 million of the OP Program's $250 million annual funding over to the Mars exploration program.

This would increase the funding of the Mars program to fully three times the total level of the Outer Planets program, despite missions to the outer Solar System being considerably harder and more expensive.

On top of this, NASA was insisting, with the support of the White House and the Office of Management and Budget that the Europa Orbiter mission was far more important.

There is, however, some evidence that OMB did so only because of private urgings from NASA management itself, based on Goldin's belief in the scientific and social importance of "astrobiological" missions in the search for life elsewhere in the our Solar System.

The cost overruns of the two missions, by themselves, would still have allowed the 2004 launch of the Pluto mission with a one or two year delay for the Europa Orbiter to around 2008-2010.

But the combination of this and the other developments led to explicit orders from NASA to cancel the 2004 Pluto launch, with NASA concentrating its resources on launching the more technically difficult Europa mission in 2006, and delaying the Pluto mission to later in the decade, if at all.

This move infuriated many planetary scientists, because -- while the Europa mission can be delayed any length of time without any loss in actual scientific data -- Pluto is virtually unique in being a scientific subject that won't wait.

Having just passed perihelion, it is moving further from the Sun in its lopsided orbit. And on top of that, Pluto's spin axis is tilted fully 60 degrees, so like Uranus it 'lies on its side" -- and, by chance, at perihelion it is almost side-on toward the Sun.

Currently one of its poles is gradually tilting further and further away from the Sun, and so an increasing surface area around that pole is being cast into permanent nighttime shadow.

This means that more and more of its surface area will be unavailable for a probe to photograph, and that the cold nighttime pole provides a growing patch of supercold surface for the atmosphere to freeze out as a polar cap, and accelerating the rate at which Pluto's atmosphere disappears.

Moreover, if the 2004 launch opportunity is missed, a Pluto-bound probe would be unable to utilize a gravity-assist flyby of Jupiter to catapult itself out to Pluto.

A Pluto mission, even if delayed only a year beyond that, will require alternate techniques to reach the planet -- probably involving both multiple gravity-assist flybys of the inner planets and some active onboard propulsion system -- which would increase the overall cost of the mission and substantially delay its arrival at Pluto, probably to about 2020 at the earliest. By which time the atmosphere will have largely frozen out.

For all these reasons, the October meeting of the SSES solidly reconfirmed its earlier recommendation that the Outer Planets Program will produce much more scientific bang for the buck if the Pluto mission is launched first, even if the Europa mission -- considered separately -- is more valuable on balance.

It also recommended that NASA should consider trying to reduce the cost of both missions by removing them from their current monopoly management by the Jet Propulsion Laboratory and select contractors through a competitive bidding process.

Despite this, all indications until now were that NASA would stick by its decision to delay the Pluto mission -- perhaps until 2009 or so -- and fly the Europa Orbiter first.

However, Louis Friedman, director of the Planetary Society, has now said in a Dec. 5 message directed both at the planetary science community and at the general public: "Whereas a few weeks ago I was pretty sure we would lose the battle for a 2004 Pluto mission, I now think a recount is in order.... We hear little wisps of Pluto in the air -- engendered by several things."

Friedman then proceeded to list his reasons:

• there is no magic bullet enabling a post-2004 direct flight to Pluto that really makes for a practical mission (not until nuclear or laser sail technology is invented)
• Europa gets harder and harder and costlier and costlier: NASA may need to delay it more, just for technical reasons; opening up an Outer Planets gap for Pluto
• And most importantly: more and more of Pluto is moving into darkness. This is a seasonal effect that is very pronounced because of Pluto's high inclination. Pluto is crossing the equinox now, but as it gets higher and higher, less and less of it will be available to see from the flyby trajectory of the probe; and it won't get better for 120 plus years. And even then, that will be worse because Pluto will be at aphelion.
• Pluto delayed is Pluto lost.

Additionally Friedman says another factor that is non-scientific, could be the deciding factor: "NASA is surprised to see how popular Pluto really is."

When Dan Goldin tentatively scheduled the Europa launch ahead of the Pluto launch two years ago, he reportedly said: "Nobody gives a damn about Pluto." But not only the scientific community, but a considerable number of the general public, apparently thinks otherwise.

Since the cancellation The Planetary Society has requested that interested people send postcards to the two Congressional committees responsible for astronautics funding.

Originally they had hoped for one or two thousand messages of support -- but they got over 10,000, all of which the Society personally delivered to the chairmen of the two committees.

Friedman has suggested that this is partly due to Pluto's mystique as "the last unexplored planet" -- and certainly as the biggest totally unexplored world left in the Solar System.

For all these reasons, NASA could be reconsidering its decision. But if such a switch occurs, it will have to be soon, or it will be too late to initiate a 2004 Pluto mission be it JPL or some other organization managing it.

Related Links
Planetary Society Petition To Save Pluto Express
Ted Nichols' "Save Pluto Express" Site
Pluto Express Mission Site
Pluto Scapes
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