Cosmic dust is exactly what it sounds like — dust in outer space. Most particles are tiny, between a few molecules to 0.1 micrometres in size. Sometimes, they make it through the Earth’s atmosphere in one piece, revealing some mysteries to astronomers about the earliest events in the solar system.
New research has shown some cosmic dust particles use bubbles as parachutes when they enter our atmosphere, and this prevents them from burning up. Dr Matthew Genge from Imperial College London found that cosmic dust particles containing water-rich minerals survive twice as often during atmospheric entry than water-free ones.
If twice as many water-rich particles make it through, that means scientists may well have been analysing a lot more of these samples, which may have given them a bit of a skewed understanding of the solar system. Genge’s results were published in the journal Geophysical Research Letters.
Normally, when something hits the atmosphere, it is travelling incredibly fast. Dust particles, for example, enter the atmosphere at about 25,000 miles per hour. Then, the travelling particles are intensely heated by collisions with molecules in the air. Many particles are turned into gas which disappears into the atmosphere.
Water-rich particles contain clay minerals or mud which have water trapped inside. When these particles enter the Earth’s atmosphere, the dust transforms into droplets of magma, or molten rock, and the water inside boils. The dust then turns into a magma foam bubble, which swells like a parachute. This slows the dust particles down quickly and decreases their temperature by 100 degrees Celsius, allowing them to survive the journey. Genge calls these parachutes “cosmic spherules.”
“Cosmic dust provides us with direct evidence of events that may have happened in our solar system billions of years ago,” Genge said in a statement. “However, our study is showing us that water-rich particles may be more likely to survive entry compared to dry ones. Scientists now need to take this into consideration when they are re-constructing ancient cosmic events or trying to develop a more accurate picture of the geological make-up of our solar system.”
In his previous work, Genge and a team discovered cosmic dust on rooftops in cities, and a lot of the stuff that makes it through the atmosphere originates from an asteroid belt between Mars and Jupiter.