Sometimes something happens that makes Earthly concerns such as the mendacity of politicians or the evil of terrorists and tyrants relatively unimportant. Such was the case recently when NASA’s New Horizons passed by Pluto and its system of moons over three billion miles away at the edge of the Solar System. Before New Horizons, Pluto was just a dot in the sky, a realm as unknown as any place in the universe. After New Horizons, the former ninth planet is a fully realized world.
The initial images of Pluto show a peach colored world with features that have been given unofficial names such as “the Heart” (recently renamed Tombaugh Region after the man who discovered the dwarf planet.) The closest images show a landscape that might be the ninth circle of Hell imagined by the poet Dante, covered with methane and nitrogen ice, but with 11,000-foot mountains made of water ice so cold and dense that it resembles bedrock on Earth. Remarkably, the surface of Pluto, which also features an ice plain, has a conspicuous lack of impact craters, suggesting that the dwarf planet is subject to geological forces the origin of which is currently unknown to science. Pluto is even active, with hydrocarbon snow and glaciers made of nitrogen ice.
As New Horizons departs from Pluto into the Kuiper Belt, that ring of ice and rock that encompasses the Solar System, the thought occurs that no one yet alive will see another new world close up. Every planet from Mercury to Pluto (albeit only a former planet) has been visited by spacecraft. The first great age of planetary space exploration, which began with the visit to Venus by Mariner 2, has concluded.
That doesn’t mean that space exploration is done. NASA is developing new hardware that could open up the Solar System to exploration as never before. Electric-powered propulsion systems, which put out a steady stream of thrust, have already sent spacecraft such as the Dawn, now orbiting the other dwarf planet, Ceres, on voyages of exploration. Those types of engines have given robotic spacecraft range and flexibility that they hitherto had not enjoyed.
Even more exciting, NASA is developing a heavy-lift rocket called the Space Launch System that could open up the outer Solar System to spacecraft such as New Horizons that will not just fly by worlds like Pluto, but orbit and even land on them. The SLS is being built to facilitate human expeditions to Mars, as well as to Earth-approaching asteroids and perhaps back to the moon. The initial model will be able to lift 70 tons to low Earth orbit with the final version being able to lift 130 tons.
The planetary science community has already noticed what such power could do to expand the capabilities of robotic explorers. NASA planners who are developing a mission to Europa, an ice-bound moon of Jupiter thought to have a subsurface ocean that might contain life, are looking at the Space Launch System to hurtle the space probe to the Jovian system in half the time that smaller rockets can manage. The SLS could accommodate a probe with sufficient mass that could orbit and perhaps even land on Europa if NASA so chose.
The kinds of missions that a heavy lifter could make possible are limited only by the human imagination though they may be limited by the willingness to pay for them. Titan, the moon of Saturn awash with liquid methane seas, and Enceladus, another moon of Saturn that spews out huge, icy geysers, are prime targets. Space enthusiasts also dream of orbiting the two other gas giants, Uranus and Neptune, each with their own system of moons.
In the meantime, scientists will spend some years digesting the rivers of data that New Horizons is sending back from Pluto. But one day, humans will want to send another probe to revisit the last world of our Solar System. Such a mission would orbit Pluto to give it and its moons a more extensive examination. Perhaps landings will be attempted on Pluto, and its equally intriguing largest moon, Charon, which bears a canyon deeper than the Grand Canyon on Earth.
The technology is there or under development. All that is required is the will. Then, New Horizons will not be the end, but the beginning of space exploration.