A team of astrophysicists has just demonstrated that the dust particles in space contain ice.
The interstellar medium—matter between the stars in a galaxy—consists of gas and dust. These particles can clump together and merge to form stars and planets. Significant chemical processes also occur on these particles, from which complex organic—possibly even prebiotic—molecules emerge.
But this whole process needs water. In specifically cold cosmic surroundings, water exists in the form of ice. But so far, the relationship between dust and ice in these regions of space was unclear.
Now, a research team has proven that ice is trapped in the dust particles in interstellar space. The team is from Friedrich Schiller University Jena and the Max Planck Institute for Astronomy.
They have described their findings in the latest issue of Nature Astronomy, a research journal.
“Until now, we didn’t know whether ice is physically separated from the dust or mixed with individual dust moieties,” explains Dr. Alexey Potapov of the University of Jena.
“We compared the spectra of laboratory-made silicates, water ice and their mixtures with astronomical spectra of protostellar envelopes and protoplanetary disks. We established that the spectra are congruent if silicate dust and water ice are mixed in these environments.”
The researchers can obtain valuable information from this data. “We need to understand different physical conditions in different astronomical environments, in order to improve the modeling of physico-chemical processes in space,” says Potapov.
This outcome would allow researchers to better estimate the amount of material. They would also make more accurate statements about the temperatures in different regions of the interstellar and circumstellar media.
Through experiments, the team from the University of Jena also noticed what exactly happens with water when the temperatures rise and the ice exits the solid body attached to and passes into the gas phase at approximately 180 Kelvin (–93 degrees Celsius).
“Some water molecules are so strongly bound to the silicate that they remain on the surface or inside dust particles,” says Potapov.
“We suspect that such ‘trapped water’ also exists on or in dust particles in space. At least that is what is suggested by the comparison between the spectra obtained from the laboratory experiments and those in what is called the diffuse interstellar medium. We found clear indications that trapped water molecules exist there.”
The presence of such solid-state water means complex molecules might also exist on the dust particles in the diffuse interstellar medium. If that’s the case, scientists may be closer to realizing complex organic molecules, for instance.
This is because the dust particles usually consist of carbon, among other things, which, along with water and under the influence of ultraviolet radiation such as that found in the environment, promotes the formation of methanol, for example. Scientists have already observed organic compounds in these regions of the interstellar medium. But until now no one knew where they originated.
The existence of solid-state water can also offer answers to questions regarding another element. Scientists are aware of the amount of oxygen in the interstellar medium. But they had no data about where exactly around a third of it lies. The results of the new study indicate that the solid-state water in silicates is a concealed reservoir of oxygen.
The ‘trapped water’ can help in understanding how the dust builds up. That’s because it could support smaller particles to stick together to form bigger particles. This effect may even work in planet formation.
“If we succeed in proving that ‘trapped water’ existed—or could exist—in building blocks of the Earth, there might possibly even be new answers to the question of how water came to Earth,” says Alexey Potapov.