After nearly nine years in space and 4.7 billion miles traveled, NASA’s Deep Impact spacecraft has met an unexpected end after mission members lost contact with it last month. Though it was unable to complete its latest assignment, the comet-hunting spacecraft led a far longer life than expected with several career changes after its first encounter with comet Tempel 1.
"We’re all saddened by the loss of the spacecraft when we were just about to get some data that should have been very interesting on comet ISON and were hoping to continue for years to come," said the mission’s principal investigator, Michael A’Hearn, an astronomer at the University of Maryland at College Park.
But, A’Hearn said, the spacecraft lived three to four times longer than its expected lifetime, and delivered information that has revealed a remarkable diversity in the cometary population and has also improved our understanding of the development of the solar system.
The mission provided researchers with an up-close and personal look at these icy, ghost-tailed time capsules of the young solar system’s chemical makeup, he added.
"Because the comets are small and cold, they preserve the chemistry that existed in the early solar system -- which nothing else does," A'Hearn said.
Ultimately, the far-traveling Deep Impact has made Earth-based studies of distant comets more reliable and powerful. Its examination of many different comets’ inner workings revealed that the composition of comets' tails looks very much like their insides – a simple but groundbreaking finding that allows astronomers to make more inferences about a comet’s interior just by studying it from afar.
Launched in 2005, the spacecraft first traveled about 268 million miles to the comet Tempel 1, where it shot an impactor into the comet’s path. The resulting collision blasted material out from beneath the comet’s surface, which the researchers were then able to study, giving them an unprecedented look into a comet’s inner workings.
Having wrapped up its planned mission in six months, NASA then put the spacecraft to work on a new mission with a brand new acronym, EPOXI (a combination of two mission names: the Extrasolar Planet Observations and Characterization, or EPOCh, and the Deep Impact Extended Investigation, or DIXI). For the DIXI portion of the mission, the team sent the Deep Impact spacecraft back past Earth to get close to the comet Hartley 2. It stayed busy during its travels with its EPOCh tasks, observing half a dozen different stars to confirm their planets’ motions.
The spacecraft also took pictures of Earth, the moon and Mars. These findings helped confirm the existence of water on the Moon, and they attempted to look for methane on Mars (in vain, as the Curiosity rover’s findings revealed this week).
The spacecraft then went on to study the comet C/2009 P1, or Garradd, in 2012 and took distant images of the comet ISON this year. But last month, around the time the mission was supposed to take close-ups of ISON, mission controllers lost contact with the spacecraft and spent several weeks trying to reactivate its systems. They finally announced that they had called it quits Friday.
While the end was unexpected, A’Hearn said, Deep Impact will likely continue to provide more scientific results as researchers pore over the data.
"We’re ecstatic with the results we’ve got so far, and we’ve still got a lot of work analyzing those data to go," he said.
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