A SHOT IN THE DARK
Chasing the aurora from the world’s northernmost rocket range
At the entrance to the mess hall, Ny-Ålesund residents abandon snow-covered shoes for cozy slippers or socks. Inside, the warm air washes over wind-whipped faces, carrying the smell of rich soups, tea, and bread. “The chef is the most important person here,” Rowland quipped.
Residents make the pilgrimage to the mess hall three times a day: first for breakfast, beginning at 7:30 a.m. sharp, then for lunch, which runs from 12:20 to 1, and finally dinner from 4:50 to 5:30. Meals are not served outside of those hours, so the mess hall’s schedule is the town’s heartbeat. It also makes for a reliable meeting ground — a place hungry colleagues gather to discuss the day’s events.
The science team sat together at a table for lunch. The launch window on the second day had just closed — another scrub — but this time it wasn’t the wind. Instead, the aurora had eluded them.
In broad strokes, all types of aurora have a similar origin story. They form when negatively charged electrons crash into the gases in our atmosphere, jarring those gases into high-energy states. As they relax back to normal they give off their excess energy in the form of light: the ruby reds and emerald greens that illuminate the northern and southern skies.
Most of these auroras are formed by the same population of electrons. These electrons come from inside Earth’s magnetic field.
But the cusp auroras — the kind that form above Ny-Ålesund for just a few hours a day — are from a different stock of electrons. When they set the sky alight, they are at the end of a 93-million-mile journey, direct from the Sun.
Most particles that flow off the Sun — collectively known as the solar wind — don’t have that fate. By and large, they are deflected around Earth’s magnetic field, sent skimming off into space. But near the north and south poles, there are two funnels where solar particles can slip inside.
These holes in our protective shield are known as the polar cusps. They’re the only places on Earth where the oncoming solar wind directly collides with our atmosphere. The polar cusps are anchored to the Sun-facing side of Earth; as the planet rotates, they remain in perpetual daylight, piping electrons from the Sun into the polar atmosphere. And between the hours of 10 a.m. and noon, the town of Ny-Ålesund passes right beneath one of them.
The cusp aurora hold secrets that extend far beyond Ny-Ålesund, both in space and time. Some 4.2 billion years ago, Mars had a hearty atmosphere along with liquid water on its surface. In its prime, scientists estimate, it might have been suitable for life. But through the millennia, the solar wind stripped Mars’s atmosphere to produce the exposed, barren landscape we see today. Partly, this is due to Mars’s weak magnetic field, which is unable to protect the planet as well as Earth’s can. Yet the story is more complicated than that, for Venus’s magnetic field is also weaker than Earth’s, yet it boasts an atmosphere 90 times thicker.
A planet’s fate lies in a complicated balancing act between countless physical processes, some that drain its atmosphere away and some that grow it. In the cusp aurora, some of these processes can be spied up close.
But Rowland is also looking to the future. Today, with just over 4,000 confirmed exoplanets, or planets orbiting stars elsewhere in the universe, the race is on to determine which of them are potentially habitable. But the dynamics of their atmospheres — which make or break their suitability for life — remain poorly understood. At present, we can do no more than make intelligent guesses, based on scientific models, about what their atmospheres might be like. To check the accuracy of these models, we test them with data collected on Earth. Data just like what Rowland’s team were here to get.
But there were no guarantees that the cusp auroras would cross their path. When the Sun’s activity is low, the cusp passes just north of Ny-Ålesund, outside of their approved launch trajectory. But a healthy gust of solar wind, they knew, could push it south, right into their path. So they waited, readying their rockets to ambush the aurora at the perfect moment.