Valentine’s Day date with a comet

Pancake-layers and a possible powdery flow are among the surface features of interest highlighted in this July 4, 2005, Deep Impact image of Comet Tempel 1. The bright flash is where Deep Impact dropped a 1.8-tonne copper projectile onto the comet. Stardust-NExT could get a first look at the aftermath of the blast.

• Stardust-NExT spacecraft to conduct fly-by of comet Tempel 1
• Second comet fly-by for Stardust, and second spacecraft encounter for Tempel 1
• Aim is to see changes in Tempel 1 since Deep Impact’s visit in 2005

BOTH COUPLES SEEMED meant for each other. There was the Stardust spacecraft, launched in 1999, and her cometary fiancée, Wild 2. Betrothed from afar, the two headed blissfully toward a 2004 rendezvous.

Meanwhile, the comet Tempel 1, making her own solitary way around the Sun in 2005, was heading toward a more explosive relationship with the Deep Impact spacecraft.

But alas, heavenly though the matches were—and fruitful, with each yielding valuable information about the evolution of the solar system—neither lasted. In 2006, Stardust tossed her dusty tokens of Wild 2 down to Earth for analysis and vowed to start anew.

She was a little older now; but with all her parts in good working order and adequate fuel, she was ready for a second mission. And Tempel 1, scarred by her violent encounter with Deep Impact, was looking for a kinder, gentler match.

The Stardust spacecraft will pass within 200 kilometres of comet Tempel 1 on Feb 14 (US time)—close enough to provide a first look at the crater caused by the Deep Impact collision (bull's eye) and a large piece of previously unmapped territory (blue).

On Valentine’s Day, the two will meet. In the heat of the moment, astronomers hope, Tempel 1 will be cajoled into yielding a few more clues about her background. And Stardust, equipped with imaging and dust composition analysis instruments, will relay those clues to Earth.

Expectant matchmakers

Among the astronomers waiting patiently are Joe Veverka, professor of astronomy and principal investigator for Stardust-NExT, the NASA mission orchestrating the rendezvous.

The Valentine’s Day flyby could yield a wealth of new information about Tempel 1’s structure and composition, Veverka said, and how its features change with every passage around the Sun.

“We know that comets lose material,” he said in a recent press conference. “But the question is, ‘How does the surface change, and where does the surface change?’” Comparing the 2005 images with the new ones—taken one rotation around the Sun later—could provide the answer.

Stardust could also catch a glimpse of the crater that formed when a probe from Deep Impact crashed into Tempel 1’s surface six years ago.

“That impact threw up so much ejecta that Deep Impact never saw the crater,” Veverka said. “So it could never see how big the crater is and what [it] tells us about the mechanical properties of the surface.”

That information is vital for any future mission that involves landing a spacecraft on the surface of a comet, he said.

And finally, astronomers hope the rendezvous will provide a closer look at some of the surface features Deep Impact saw when it zoomed by in 2005. Layered terrain, for example, could contain information about how comet nuclei were formed; and smooth flows hint at some internal processes that could be working their way up to change the surface.

“Deep Impact saw only about one-third of the surface,” Veverka said. “We would like to see more.”

Stardust-NExT's first glimpse of Tempel 1, taken on January 18-19, 2011.

So, as February 14 approaches and other romantic souls plan candlelight dinners, Veverka and colleagues are tracking the pair, now hurtling toward each other at about 590,000 miles a day.

Stardust caught its first glimpse of Tempel 1 on January 26. It will keep its eye on the comet as it approaches, collecting data to help mission navigators refine its trajectory.

Close encounter

And on Valentine’s Day, as Earthbound lovers gaze into each other’s eyes, the two orbiting bodies will meet, about 120 miles apart. As they pass, Stardust will test the density and composition of the dust surrounding the comet and snap 72 high-resolution images.

(Note: the fly-by is due to occur at 11:37pm, US EST on February 14, which is 3:37pm February 15 Sydney time.)

Researchers expect to receive the data within a few hours of the closest encounter. “The science team is awfully excited,” Veverka said.

And thus, perhaps, the curtain will close on this cometary encore. But as with all concluded affairs, there will be months—perhaps years—of data analysis; and ultimately, plans for the next mission.

“Comets preserve some of the most faithful information about what happened when the Solar System formed,” Veverka said. “This is a step toward the ultimate answer.”

Follow Stardust-NExT on Twitter

Follow the comet encounter live on NASA TV

Stardust-NExT facts:

Stardust mission: Approved by NASA in 1995 for mission to comet Wild 2

Spacecraft manufacturer: Lockheed-Martin Aeronautics

Launch vehicle: Boeing Delta II rocket

Launch: February 7, 1999 (as Stardust)

Asteroid Anne Frank flyby: November 2, 2002

Comet Wild 2 flyby: January 2, 2004

Sample capsule return: January 15, 2006

July 3, 2007: Stardust approved for NExT mission to comet Tempel 1

Comet Tempel 1 flyby: February 14, 2011

Electrical power: Generated by solar panels

Kilometres travelled: About 5.8 billion

Adapted from information issued by Cornell University / NASA / JPL-Caltech.

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