A Year on Neptune and the Future of Space Exploration

According to a news report the other day, as of July 11, it's been one year since the planet Neptune was discovered; one year on Neptune, that is. This sounds about right, since Neptune was discovered on September 23, 1846, and the planet takes 164.79 Earth years to orbit the Sun. The idea that a single year could last that long is fairly mind-boggling to most people, though it is not even close to being the most incredible statistic astronomy has to offer. Neptune itself, the most distant of the large planets in our solar system, is a fascinating place, and the story of its discovery is equally fascinating, though too long to relate here (incidentally, though Neptune was only recognized as a planet in 1846, it was observed several times before by astronomers who took it for a star, the earliest and most notable being Galileo Galilei). Neptune, like Jupiter, Saturn, and Uranus, is a gas giant planet, with a radius almost four times that of Earth and a mass of more than 17 times that of Earth. It is blue in color, has a faint ring system, and thirteen known satellites, most notably the large moon Triton. Neptune orbits the Sun at a distance of 4.5 billion km (compared to about 150 million km for the Earth).

There is still much to learn about Neptune, as well as about the even more distant objects beyond it, such as the small planets (or dwarf planets, if we accept the IAU's reclassification) Pluto and Eris (though it has been over 80 years since Pluto's discovery, only a third of a Plutonian year -- which lasts 248 Earth years -- has passed since it was identified). While a spacecraft is on its way to Pluto and its companion Charon, there are no other such missions scheduled, so we may have to settle for studying Neptune (which was visited once by a spacecraft, Voyager 2 in 1989) and other objects in the outer solar system from a distance for quite some time into the future.

While it may be a long time before any more robotic spacecraft visit Neptune, and even longer before humans get anywhere near it, there are a lot of other places in the solar system that we should be trying to get to in the next few decades, by robotic craft or even with human-crewed missions. Among them are Jupiter's moon Europa, Saturn's moon Titan, and of course Mars and the asteroids (the latter two being the near-term goals for human space exploration, along with the Moon). The problem, as usual, is getting enough funding for the missions (even though as I've pointed out elsewhere, space exploration costs far less than a lot of other things we spend money on, whether it's the US government spending money on the military or the general public spending it on sports or cosmetics). Many people are regrettably short-sighted about such things, not only politicians but people in the media as well.

For an example of the latter, take the recent issue of the Economist which featured a cover showing the space shuttle in flight and the title "The End of the Space Age". The cover refers to the other, much more widely reported space-related milestone of the past few days, the launch of the last space shuttle mission. The magazine's lead editorial declared human space exploration dead or at least almost so, and seemed to give the impression that this was a good thing. I disagree, of course, and so I sent a rather rapidly written but hopefully coherent response, which I will conclude this blog entry with:

Your editorial on the future of space exploration was regrettably short-sighted and unimaginative. I take issue not so much with your view of the near-term problems faced by human space exploration, particularly the budget difficulties hindering any major endeavors such as a return to the Moon or sending humans to Mars, as they are formidable. But I do disagree with your view that this hiatus in space exploration by humans is anything other than temporary (absent a disaster on Earth that is destructive to human civilization as a whole), and I certainly take exception to your implication that this is a good thing, made most obvious by your dismissively referring to advocates of space exploration as "space cadets".

The benefits brought by space exploration, whether human or robotic, have been numerous, but near-term "practical" benefits are not, or at least should not, be the main driver behind sending people into space, or for that matter behind any scientific endeavor. People like Archimedes, Galileo, Newton, and Einstein did not do science because they were concerned about practical applications to their work. It is part of human nature to be curious about the unknown and so to explore new places. What's more, this type of exploration is highly inspirational. How many of today's leaders in the fields of science and information technology were inspired to take up their current careers by seeing humans walk on the Moon? A human mission to Mars could do the same for a new generation.

Furthermore, if we take a long-range view, there is a lot to be gained in human expansion into the rest of the solar system. Whether we talk about mining, testing cutting edge technologies, or even settling permanently on Mars or elsewhere, human space exploration will someday pay for itself. Of course that day is far in the future, and in the meantime a large upfront investment is necessary. But why should humanity restrict itself to thinking in terms of the next decade or even the next generation? There is no reason we cannot invest in something that will bear fruit a century from now (indeed, we had best learn to think in such long-range terms if we hope to deal with climate change).

Finally, your observation about "diminishing returns" from robotic exploration reveals a misunderstanding about the purposes and status of such exploration. The goal was never simply to visit as many places as possible to add them to the "stamp album". The goal has always been to learn as much about our neighborhood as we can, to answer all sorts of questions about our surroundings and our origins. What we have learned in many cases makes it more imperative, not less, that further exploration be made. Is the ocean under Europa's icy crust home to life? How about Saturn's massive moon Titan with its thick atmosphere and its hydrocarbon lakes and seas? Is there now or has there in the past been life on Mars? Only further exploration by robots or humans can answer these questions and many more. Perhaps the current generation will indeed prove too short-sighted to care, but eventually the natural drive to explore will drive us out away from Earth.