A new decade is dawning and it will be a bold one with spacecraft expected to visit both reaches of the Solar System and the many worlds in between. There have been many great discoveries and stunning revelations; the decade ahead should be ripe with even more. The following are the discoveries that the author feels will be made by 2020.

Water ice is discovered on Mercury. MESSENGER will begin orbiting Mercury on March 18, 2011 for at least one year of exploring and perhaps for several additional years. The craters near the poles that are in eternal darkness are a frigid -300ºF and radar observations from Earth have hinted at the possibility of ice in these craters. Comets contain water and their impacts on Mercury deliver water to the surface, but at 800ºF in the sunlight it is far too hot for water to exist in any form. Near the poles the conditions are more favorable for water to exist in the form of ice. MESSENGER should be able to determine once and for all if there is water on Mercury.

Active volcanoes are discovered on Venus. A pressurized inferno perfectly describes Venus where surface temperatures can exceed 900ºF, the pressure exceeds Earth’s 90 times and the atmosphere is laced with a sulfuric acid mist. Prior missions revealed that Venus had a violent volcanic history with nearly the entire planet resurfaced in a wave of volcanic eruptions around 600 million years ago. Unusual spikes in the atmospheric concentrations of sulfur dioxide and lightning clustered around several of the many volcanic peaks hint that Venus is currently volcanically active, but the thick cloud cover prohibits any direct viewing. The Venus Climate Orbiter, known as Akatsuki, is a Japanese mission that plans to listen to Venus’ atmosphere with a sophisticated sounder that should detect the rumbles of thunder from both lightning and erupting volcanoes. It will also measure the surface temperature with high precision and hopefully reveal volcanic hot spots. Missions that have yet to be approved by the U.S. and Russia may fly during the decade and will increase the chance for this crucial discovery. We may be awed by a world as violently volcanic as Jupiter’s moon Io.

Liquid water is discovered beneath Ceres’ surface. Asteroids are not all boring; the more we explore them, the more interesting they become. Ceres is the largest asteroid with a diameter of about 605 miles and is classified as a dwarf planet because it is round. Observations from Earth indicate that Ceres is unusually rich in water and unusually warm with a surface temperature as warm as 0ºF in the sun. There is a hint of a thin atmosphere and this all points to the possibility that it is a water-rich asteroid with a warm interior. It may be warm enough on Ceres for the water to exist as liquid and there may be enough to fill Lake Erie! Dawn is a U.S. asteroid mission that will first reach Vesta during July 2011 and orbit it until July 2012 before flying off to Ceres. It will arrive at Ceres during February 2015 and will orbit it until at least July 2015, and hopefully longer, at least until the spacecraft fails from old age. Dawn will make detailed measurements of the surface features, minerals, temperature, composition, gravity, and any possible atmosphere at both asteroids. If Ceres has geysers, they will be detected and imaged. If there is liquid water beneath its crust, Dawn will be able to detect and measure it. Liquid water will be a major discovery for an asteroid and will make scientists rethink the theory of the creation and evolution of the asteroids.

Lightning is discovered on Titan. The Cassini orbiter mission around Saturn has already gone into the history books as one of the most beautiful and productive planetary missions ever flown. The discoveries of geysers on Enceladus and methane lakes on Titan are two of this past decade’s greatest discoveries. Huygens gave us our first direct look at Titan from its surface on January 14, 2005 when it landed in a vast mudflat where liquid methane may have recently flowed. Cassini discovered large billowing clouds that are raining methane and filling lakes. The clouds grow and dissipate over time and there are also lake effect clouds blowing downwind of Titan’s largest lakes, which rival seas being larger than Lake Superior. This proves that Titan is a world of wind and weather in spite of its frighteningly cold surface at -290ºF. Cassini is now in an extended mission that will last until September 2017 while the seasons are changing on Titan. The northern hemisphere is heading into spring while the southern hemisphere heads into autumn. Each season lasts seven years because Saturn orbits nearly a billion miles from the Sun and takes about 29 years to orbit. This gives plenty of time for the weather to evolve on Titan and it may be possible to watch large convective clouds multiply and grow to the point where they would develop into thunderstorms or at the very least contain a few intermittent flashes of lightning. Titan is a frozen version of a prebiotic Earth and the discovery of lightning will be one of the decade’s biggest discoveries, because lightning can synthesize complex organic compounds, which is thought to be a precursor to life.

Geysers are discovered on Pluto. It no longer matters if Pluto is a planet as it will prove to be an active and evolving world when New Horizons flies past it on July 14, 2015. Pluto has a thin atmosphere with hazes and possible clouds, but it is expected to freeze out onto the surface as Pluto moves away from the sun to the distant part of its orbit by 2113 when the surface temperature will plummet from -380ºF to -420ºF. The atmosphere is a frigid mixture of methane, nitrogen, carbon monoxide, argon, and other gases while the surface is covered with methane and nitrogen frost similar to Neptune’s moon Triton. Voyager 2 discovered geysers on Triton when it flew by it on August 25, 1989 and it has been speculated that Pluto may also have active geology with erupting geysers that help to create Pluto’s atmosphere. If there was no spacecraft headed to Pluto, the geysers could still be indirectly discovered from Earth since Pluto’s atmosphere would not completely freeze out onto the surface because the geysers would continually replenish at least a fraction of the atmosphere. The discovery of geysers erupting on Pluto by New Horizons may provide the decade’s most dramatic and fascinating images returned by any spacecraft.

“To boldly go where no man has gone before” is a popular Star Trek phrase. Mankind has yet to travel any farther than the Moon and has stayed primarily in low Earth orbit. It is our unmanned spacecraft that boldly go where nobody has yet to go and perhaps never will. It will be these spacecraft that will continue to awe all of us with their discoveries, the predicted and unpredicted.