Exploring the Stars: How NASA's ISS Unveils the Mysteries of Polar Lights

In January 2025, the NASA astronaut and veteran space photographer Don Pettit posted a short video from the International Space Station with the caption “Flying over aurora; intensely green.” What he had filmed was not the aurora everyone on the ground knows — the curtain of light hanging overhead — but the same phenomenon seen edge-on and from within, the station threading through the top of the glowing sheet at roughly 28,000 kilometres per hour. Pettit later described the sensation of being able to fly into the auroras as “like being shrunk down and put inside of a neon sign.” That single change of vantage point — from underneath to alongside — is what makes the ISS such an unusual instrument for studying polar lights.

What the station actually is

The International Space Station is not a telescope pointed at deep space; it is an inhabited laboratory in low Earth orbit, circling at an altitude of roughly 400 kilometres and completing a lap of the planet about every ninety minutes. Its first module, the Russian-built Zarya, launched in November 1998, and the outpost has been continuously crewed since 2 November 2000 — meaning that as of the mid-2020s there has not been a single day in nearly a quarter of a century without at least one human living off the planet. It is operated jointly by five space agencies: NASA of the United States, Roscosmos of Russia, JAXA of Japan, ESA representing much of Europe, and CSA of Canada, an arrangement that survived considerable geopolitical strain precisely because dismantling it would have been harder than keeping it running.

That relentless, unbroken occupation is quietly one of the station’s most remarkable engineering achievements. Keeping a complex system alive and staffed for 24 years without interruption is a discipline more familiar to infrastructure engineers than to the public — the same obsessive attention to redundancy and continuous operation that, on a far humbler scale, someone chasing near-perfect uptime on a home server cluster will recognise. The stakes differ enormously, but the mindset — assume things will fail, build so the whole never does — is the same.

What the aurora actually is

To appreciate why the orbital view matters, it helps to be precise about the physics, which the older folklore got poetically wrong. Auroras are produced when charged particles — chiefly electrons — from the solar wind are funnelled down Earth’s magnetic field lines toward the poles and collide with atoms and molecules in the upper atmosphere. Each collision excites an atom, and as it relaxes it releases a photon of a specific colour.

The familiar green comes from atomic oxygen, energised at altitudes of roughly 100 to 150 kilometres. The rarer, ghostly red is also oxygen, but excited far higher — up to around 400 kilometres, which is essentially the ISS’s own altitude. Blues and purples come from nitrogen lower down. This is why the aurora is not a flat sheet but a three-dimensional structure with height: different colours are literally emitted at different levels of the atmosphere, and from the ground we see them stacked and foreshortened into a single glowing veil.

The shapes matter too, and they are not random. The rippling curtains, arcs and spiral folds trace the invisible lines of Earth’s magnetic field, which is why the aurora so often looks like fabric caught in a wind — the “wind” being the magnetic field itself, being buffeted by the incoming solar particles. During a strong geomagnetic storm the whole structure can brighten, expand toward the equator, and pulse in waves, as the magnetosphere absorbs and releases energy in fits. What looks like an idle light show is a real-time readout of forces playing out hundreds of kilometres overhead, and reading those shapes correctly is part of how scientists reconstruct what the Sun did days earlier.

Why the orbital vantage point changes the science

From the surface, we look up at the underside of the aurora and see it flattened against the sky. From the ISS, astronauts look down and across it, seeing its vertical structure directly — the way the green base sits below the red crown, the way the curtains ripple and braid along the magnetic field lines. That geometry is not merely prettier; it lets researchers correlate the shape and colour of the light with the physical altitude at which it is being produced, in a way a ground observer simply cannot.

The station also passes through the aurora’s upper reaches during geomagnetic storms, which turns it into an in-situ probe: instruments on board can sample the very particle environment that is producing the display, rather than inferring it from afar. Combined with dedicated magnetospheric satellites, this helps scientists refine their models of how solar activity couples into Earth’s magnetosphere — the same models that underpin space-weather forecasting for power grids, GPS and radio communications. The aurora, in other words, is the visible symptom of an invisible system whose disturbances have very practical consequences on the ground.

Space weather, and why it is not just scenery

The aurora is beautiful, but it is also a warning light on the dashboard of a system that can cause real damage. The same solar activity that brightens the polar sky — coronal mass ejections and gusts in the solar wind — can, when strong enough, induce currents in long conductors on the ground and disturb the upper atmosphere in ways that matter to modern infrastructure. The reference case is the Carrington Event of September 1859, the most intense geomagnetic storm on record, during which auroras were reported as far south as the Caribbean and telegraph systems failed, sparked and in some cases shocked their operators. A storm of that magnitude striking today’s grid- and satellite-dependent civilisation is one of the scenarios space-weather agencies plan against.

Closer to living memory, in March 1989 a geomagnetic storm knocked out the Hydro-Québec power grid in Canada, leaving millions without electricity for around nine hours. Solar storms can also swell the upper atmosphere enough to increase drag on satellites — including the ISS itself, which occasionally has to fire thrusters to maintain its orbit — and can degrade GPS accuracy and high-frequency radio. Studying auroras from orbit is therefore not idle sightseeing; it feeds directly into the models that forecast these disturbances. When the station passes through the auroral zone during a storm, its onboard sensors sample the particle environment at the exact altitude where the effects begin, giving researchers ground truth that satellites at other orbits cannot supply.

From omen to instrument

For as long as people have lived at high latitudes, the lights have demanded explanation. In Old Norse cosmology the shimmering was sometimes linked to Bifröst, the burning rainbow bridge between the realm of humans and that of the gods. Several Inuit groups of the Arctic told that the lights were spirits of the dead — in some tellings, playing a ball game with a walrus skull across the sky. What these accounts share is an attempt to read meaning into a sky that behaves like nothing else on Earth. The scientific account, worked out only over the last century or so, does not diminish that impulse; it simply relocates the wonder from the supernatural to the electromagnetic. The story of how the lights were finally explained — from folklore to solar wind — is one worth following on its own, and it is told in detail in our guide to chasing the aurora borealis.

Fun facts

• Because the ISS orbits at around 400 kilometres, it sits at roughly the altitude where the rare red aurora is produced — astronauts sometimes photograph the station skimming the very top of the glowing curtain rather than looking up at it.
• The station laps the Earth about every 90 minutes, so a crew can witness roughly sixteen sunrises and sunsets in a single day, and pass over the auroral zones many times in one shift.
• The green of a “normal” aurora and the red of a rare one are both emitted by oxygen — the difference is purely altitude and how the atoms are energised, not a different element.
• The ISS has been continuously inhabited since 2 November 2000, an unbroken human presence in space that has now outlasted several of the political relationships between the countries running it.
• Astronaut Don Pettit is as well known for his photography as his science; his long-exposure and time-lapse imagery of auroras and city lights has done as much to popularise orbital science as many formal outreach programmes.

Closing reflection

There is a neat symmetry in the fact that the ISS orbits at almost exactly the height where the aurora’s rarest colour is born. For most of history the lights were something humans looked up at and invented stories to explain; now there are people who fly straight through them, cameras running, close enough to describe the experience as stepping inside a neon sign. The mystery has not been abolished so much as approached from a new angle — and it turns out that getting closer to a wonder, rather than dissolving it, mostly just reveals how much structure was hiding inside the glow all along.