In 2004, a NASA spacecraft called Stardust captured the first ever samples from a comet, named Comet Wild 2. It returned these samples to Earth in January 2006 – and new analysis of the samples is revealing what type of particles the spacecraft collected.
Stardust gathered the samples by using blocks of an ultralight material called aerogel and flying through the tail of the comet, with cometary particles impacting the gel at 21,600 kilometers per hour (13,420 mph). Speaking at the 227th meeting of the American Astronomical Society in Florida, student Amanda White from the American Museum of Natural History in New York – who is conducting new research on the samples – explained that examining the shape of the dents in the gel could reveal new insight into their origin.
"We can estimate the size of the original particle, just by looking at the entry hole of the track. But we think we can do better than measuring the hole," she told the BBC. "We essentially want to do the same thing as what they do in a crime show, when they're doing ballistics."
The research is ongoing, and it’s possible that the size, consistency, and composition of the original grains could be determined – giving new insight on the comet itself. Most notably, ice and gas from the comet evaporated before it made it back to Earth. But the shape of the impacts on the gel could indicate that some of these so-called volatiles struck it, hinting at the comet’s composition.
Shown are some of the tracks from comet dust particles in the aerogel. NASA
To make their findings, the team is using a confocal microscope to recreate the samples in 3D, in addition to using a particle accelerator known as a synchrotron to measure the chemical composition of the samples.
Understanding comets like this is key to improving our knowledge of the early Solar System. Wild 2, which orbits between 1.592 and 5.308 AU (astronomical units, 1 AU is the Earth-Sun distance) formed 4.5 billion years ago in a more distant orbit, but it was pulled into the inner Solar System by Jupiter in 1974, giving NASA an opportunity to explore it. Though designed to collect cometary particles, analysis of the samples has already revealed the presence of interstellar particles.
Other comets, like 67P/Churyumov-Gerasimenko, have provided information on the role of comets in the origin of the Solar System. Perhaps Wild 2 will also have a part to play.
The video below shows off one of the 3D recreations.
