Robots That Have Collected Interstellar Dust: Photos

Here are some of the intrepid spacecraft who have joined the 'interstellar dust club' and picked up particles from outside the solar system.

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Can you find something physical from interstellar space while not leaving our solar neighborhood? It turns out that interstellar dust particles rain down upon the solar system and, luckily for us, a few plucky spacecraft have captured these invaluable grains. One spacecraft even returned them to Earth for further analysis. Just as NASA's Cassini mission joins the "interstellar dust club," here are some more intrepid machines that have picked up dust from beyond the solar system.

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Image: Artist's impression of NASA's Cassini mission flying past icy Saturn moon Enceladus when collecting particles of dust. Earlier this month, scientists realized that Cassini had picked up more than particles produced by Enceladus.

Ulysses was a spacecraft designed to look at the sun as well as the regions above and below the sun's poles. To get there, however, the spacecraft took a bit of a circuitous route. It lifted off into space on NASA's space shuttle Discovery on Oct. 6, 1990. From there, it was released from the cargo bay and flew out towards Jupiter to get a planned gravity assist up and over the sun's poles. More than a year later, on Feb. 8, 1992, Ulysses came within about 446,000 kilometers (277,000 miles) of Jupiter. There it found some dust, with a frequency of about once a month,

NASA said

. The dust was believed to either come from Jupiter itself or its volcanic moon, Io. But it also found different dust -- bigger particles moving opposite to how the planets move. This was the first time that dust particles from beyond our solar system were detected.

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Image: Artist's impression of Ulysses and Comet Hyakutake, which whizzed into the inner solar system in 1996.

Galileo was the first mission to stay at Jupiter for the long term. It also left Earth on a space shuttle (Atlantis) on Oct. 18, 1989. From there, the spacecraft had gravity assists at Venus and Earth to swing it out to Jupiter, where it remained until 2003. At the end of its mission, scientists deliberately boosted the spacecraft into Jupiter to avoid contamination with a potentially life-friendly moon, like Europa. The Galileo spacecraft

saw more interstellar dust

as it moved from Earth to Jupiter, confirming Ulysses' find. In 1998, scientists

published a study in the journal Science

saying that they had found a new dust ring around Jupiter that moves backward to the planet's orbit. Based on some dust collected by Galileo, the researchers said that the dust is a combination of interplanetary and interstellar particles.

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Image: In this artist's impression, the Galileo spacecraft passes close to Jupiter's moon Io (left). Jupiter is in the background.

Stardust left Earth in 1999 on board a Delta II launch vehicle at the Cape Canaveral Air Force Station in Florida. Its primary mission was to fly by Comet Wild 2 in 2003 and to pick up a sample; one portion of the spacecraft returned with the sample in 2006, while the other continued on to view Comet Tempel 1 in February 2011. One month later, scientists deliberately burned through Stardust's remaining fuel (ending the mission) to gain information to to better estimate fuel levels in future spacecraft. Analysis of the dust particles collected continues, which led to a potentially exciting find in 2014. Tentatively speaking, seven interstellar dust particle tracks were identified in Stardust's aerogel collector. The collector was mounted in a location opposite to another one that picked up particles from Comet Wild 2. Dozens of particle tracks were identified, but most of them were ruled out as spacecraft debris,

according to


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Image: Artist's conception of the Stardust spacecraft encountering Comet Wild 2.

The Cassini spacecraft launched from Earth in 1997 and made flybys of Venus and Earth before arriving at Saturn in 2004. It has remained there ever since, taking the first extended close-up look at the gas giant and its many moons. The spacecraft's mission is expected to end next year when Cassini flies into Saturn. This will provide scientists more insight on Saturn's internal structure, and protect Saturn's icy moons from potential contamination should the spacecraft land on one. Earlier this month, the Cassini spacecraft also made an interstellar dust detection using its dust analyzer instrument. Most of the particles it collects is from the geyser-spewing Enceladus, but 36 of them appeared different. These particles were travelling faster and on a different path than what is usually detected, NASA said, a strong indication that they are indeed from interstellar sources.

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Image: Artist's impression of dust grains around Saturn.