Those moments when a spacecraft turns a faint and distant point of light in the night sky into a newly seen world are among the most sublime that astronomy can offer.
Not perhaps as grand as Magellan or Columbus sighting the New Worlds of terrestrial exploration, which wild and terrifying though they may have been, shared a breathable atmosphere, and the same manageable force of gravity as the Old World, and were inhabited by fellow indigenous peoples and cultures to exploit, crush, and even exterminate.
Space flight to the outer worlds is thus strangely pure of heart and mind. It’s all about inquiry, curiosity, and technologies, that may one day bring our species around the corner of some cosmic river, where, as some sci fi writers have suggested, we might end up looking and feeling like our ancestors would have if they had paddled their canoes slowly into modern Manhattan at peak hour, and become lost in the subway.
There will be two such moments this year, to add to the ongoing Rosetta comet mission, and the Mars Rovers, lead by Curiosity. In July NASA’s New Horizons instrumented cannonball will rip through the weird mini planetary system which is Pluto, plus assorted moons, and stuff we might not see until it is too late to avoid, giving up a collection of new and complex objects at a resolution that makes that transition from faint specks on the canvas into real micro worlds.
But first comes Ceres. This week produced views from the ion-engine propelled Dawn spacecraft of this giant in the asteroid belt at a higher resolution than was previously possible with the Hubble Space Telescope.
Dawn will not enter its initial and ever closer orbits around Ceres until March but already it shows signs of impact craters and at least two unusually bright spots, one apparently surrounded by spikey rays of ejected material that might contain icy material.
Ceres is an oblate object, wider in radius at its equator at about 487 kms than between its poles, at 454 kms. It is calculated to contain about 30 percent of the total mass of the thousands of other objects in the solar system’s main asteroid belt between Mars and Jupiter, but is it really an asteroid?
Vapour, possibly water vapour, has been detected as coming off its surface. It has been estimated that Ceres may contain as much water as half of this world’s natural fresh water reserves which are primarily held in the glacial vastnesses of Antarctica and Greenland. However there is a huge difference between ices that may sublimate into traces of hydrogen and oxygen but contain all sorts of other chemical combos and ‘fresh water’. Sparking ice water or ice cubes from Ceres might not become the power cocktail ingredient of choice at the trendy earth orbiting bars of the twenty second century after all.
Whether Ceres is more like a comet or an asteroid is a question that used to be asked quite commonly before the Rosetta probe and its lander Philae reached Comet Churyumov-Gerasimenko last year, destroying the conventional view as to what comets are anyhow.
Dawn may well spring similar surprises about Ceres, as it will orbit it for many months from early March, and quite possibly, attempt a very slow crash landing on the surface once its supplies of propellant for orbital adjustments approach loss of control levels.
(This is a remarkable space craft in its own right. It was launched on its long duration mission in 2007 and relies on a low power but long endurance ion-propulsion system to shunt itself in slow motion through the asteroid belt, where it it first went into temporary orbit around the large rocky asteroid Vesta before moving on to Ceres.)