Nevertheless, he explains, there have already been some surprises. “We found minerals in the cometary sample that form only at very high temperatures. This is a puzzle because the comet formed at the edge of the young Solar System, which wasn’t any warmer than 30 Kelvin. What are these high temperature rocks doing in the comet? The implication is that they formed close to the early Sun and were transported out to the edge of the Solar System before the comet formed. We thought most of the flow in the early Solar System was inwards towards the Sun, so it’s a puzzle as to how this material ended up in those cold outer regions. This is one of the biggest surprises of the mission so far.”

But the deeper analysis is just getting started. “This is going to be going on for many, many years,” says Westphal. “We have to be very careful with the interstellar samples because it’s unlikely that we’re going to be getting any new stardust any time soon. The biggest particles that we’ve found are two microns across and weigh about a trillionth of a gram, so about a trillion of them would fit into a teaspoon. We’re really pushing the limits of analytical techniques.”