For the very first time, water vapor has been detected on an object in the asteroid belt, providing definitive proof that Ceres, the dwarf planet, contains both an atmosphere and a surface of ice. If that ice were to melt, scientists postulate, the tiny planet only 590 miles in diameter may possibly contain more freshwater than all of Earth.
The discovery, published in the journal Nature on Wednesday, was made by a team at the European Space Agency (ESA) under the Herschel mission, using the infrared telescope of the same name -- the largest, most powerful ever to fly in space -- to help scientists study the evolution of the universe and its various celestial components. Herschel also is pivotal in contributing to coinciding NASA projects, namely the mission seeing the Dawn spacecraft to Ceres at this very moment.
"We've got a spacecraft on the way to Ceres, so we don't have to wait long before getting more context on this intriguing result, right from the source itself," Carol Raymond, the deputy principal investigator for Dawn at NASA's Jet Propulsion Laboratory, said in a press release on the discovery. "Dawn will map the geology and chemistry of the surface in high-resolution, revealing the processes that drive the outgassing activity."
Scientists have long thought that Ceres -- once known as a large asteroid and first spotted back in 1801, but renamed a dwarf planet due to its immense size in 2006 -- contained a surface of water, ice, and various minerals. The findings published Wednesday have finally confirmed this. "This is the first time water vapor has been unequivocally detected on Ceres or any other object in the asteroid belt," said Michael Kuppers, lead author of the Nature paper and a member of the ESA in Spain.
It did take a few trials and some guesswork to make up for detection discrepancies. Herschel did not detect water vapor every time it looked upon Ceres, leading scientists to theorize that as the dwarf planet swung closer to the sun, sections of the surface warmed, causing plumes of water vapor to shoot out at a rapid rate for select amounts of time that varied depending on the time and date.
Thanks to that varying rate, the group was able to hone in on the plumes' source: two dark spots on Ceres that were previously detected by NASA's Hubble Space Telescope. The dark spots may be the source of the water vapor plumes, the paper notes, because those sections of the surface are more likely to warm faster than lighter portions.
A more complete understanding of what is happening on Ceres' surface will come from Dawn, which is slated to arrive in the planet's orbit in the spring of 2015. Having come from the asteroid belt's second-largest object, the protoplanet Vesta, Dawn will become the first spacecraft to orbit two extraterrestrial bodies.
Still, even before Dawn's arrival, scientists are advancing our understanding of the solar system -- thanks to the Herschel discovery -- regarding how distinct objects like Ceres formed, moved throughout its lifespan, retained ice, and interacted with high-gravity objects like Jupiter that play a key role in forming regions like the asteroid belt.
"We now have a more sophisticated model for the evolution of the solar system called the Nice model, which successfully explains many of the features of the solar system, with the planets having migrated outwards and then maybe also inwards," Kuppers said in an interview with the BBC.