Artist rendering of Stardust-NExT spacecraft nearing comet Tempel 1.
Credit: NASA
MARYLAND: NASA is about to discover how solar heat devours a comet, using the Stardust-NExT spacecraft to revisit the comet Tempel 1. The two visits bracket one complete orbit of the comet around the Sun - and a blast of solar heat.
"For the first time, we'll see the same comet before and after its closest approach to the Sun," said Joe Veverka, principal investigator for NASA's Stardust-NExT mission.
"Close encounters with the Sun never go well for a comet," said Veverka. "Fierce solar heat vaporises the ices in the comet's core, causing it to spit dust and spout gas. The cyclic loss of material eventually leads to its demise."
Going back for more tantalising glimpses
Researchers suspect the flamboyant decay doesn't happen evenly all over a comet's surface, but until now they've lacked a way to document where, exactly, it does occur.
On February 14 Stardust NExT will image some of the same surface areas Deep Impact photographed six years ago, revealing how these areas have changed and where material has been lost. NASA's Deep Impact probe visited Tempel 1 in 2005.
"Deep Impact gave us tantalising glimpses of Tempel 1," said Veverka. "And we saw strange and unusual things we'd like a closer look at."
Comet’s surface layered like pancakes
At a January 2011 press conference, Veverka and other Stardust-NExT team members listed the features they're most interested in seeing again. For starters, parts of the comet's surface are layered like pancakes.
"Earth has layers because water and wind move dirt and debris around here, but layering on a comet was a surprise – and a mystery," said Veverka. "One idea is that two protocometary bodies collided at low speeds and smushed together to form something like a stack of flapjacks," says Pete Shultz, Stardust-NExT co-investigator.
Data obtained by Stardust-NExT will provide clues and possibly reveal what made the "comet pancakes."
A fuzzy ball with a history
Another area intrigues the research team even more. "There's a large plateau that looks like a flow," said Shultz. "If it really is a flow, it means there was recently gas and dust emanating from the [surface]."
Stardust-NExT will reveal how the plateau has changed, helping the team determine its origin. Whatever their origin, the plateau and layering show that comets have a much more complicated geologic history than previously thought. "Tempel 1 is not just a fuzzy ball," said Shultz. "It has history."
It's a history NASA has had a hand in. During its 2005 visit, Deep Impact dropped an 820-pound projectile into the comet's core. In a development that surprised mission scientists, the impact excavated so much material that the underlying crater was hidden from view.
Deep Impact's cameras were unable to see through the enormous cloud of dust the impactor had stirred up. Stardust NExT could provide a long anticipated look at the impact site.
