Changing chemistry
None of the researchers aboard the business jet turned scientific laboratory that took off from Easter Island in September got to see the moment when Cluster Salsa burst into a fireball above the deep, dark waters of the Pacific Ocean. Against the bright daylight, the fleeting explosion appeared about as vivid as a midday full moon. The windows of the plane, however, were covered with dark fabric (to prevent light reflected from inside to skew the measurements), allowing only the camera lenses to peek out, says Jiří Šilha, CEO of Slovakia-based Astros Solutions, a space situational awareness company developing new techniques for space debris monitoring, which coordinated the observation campaign.
“We were about 300 kilometers [186 miles] away when it happened, far enough to avoid being hit by any remaining debris,” Šilha says. “It’s all very quick. The object reenters at a very high velocity, some 11 kilometers [seven miles] per second, and disintegrates 80 to 60 kilometers above Earth.”
ESA
The instruments collected measurements of the disintegration in the visible and near-infrared part of the light spectrum, including observations with special filters for detecting chemical elements including aluminum, titanium, and sodium. The data will help scientists reconstruct the satellite breakup process, working out the altitudes at which the incineration takes place, the temperatures at which it occurs, and the nature and quantity of the chemical compounds it releases.
The dusty leftovers of Cluster Salsa have by now begun their leisurely drift through the mesosphere and stratosphere—the atmospheric layers stretching at altitudes from 31 to 53 miles and 12 to 31 miles, respectively. Throughout their decades-long descent, these ash particles will interact with atmospheric gases, causing mischief, says Connor Barker, a researcher in atmospheric chemical modeling at University College London and author of a satellite air pollution inventory published in early October in the journal Scientific Data.
Satellite bodies and rocket stages are mostly made of aluminum, which burns into aluminum oxide, or alumina—a white, powdery substance known to contribute to ozone depletion. Alumina also reflects sunlight, which means it could alter the temperature of those higher atmospheric layers.
“In our simulations, we start to see a warming over time of the upper layers of the atmosphere that has several knock-on effects for atmospheric composition,” Barker says.
For example, some models suggest the warming could add moisture to the stratosphere. This could deplete the ozone layer and could cause further warming, which in turn would cause additional ozone depletion.