In a recent study, scientists used planetary atmospheres as a new search strategy for dark matter, focusing on the production of ionizing radiation.
Search for Elusive Dark Matter
Eighty years ago, experts first suspected the existence of dark matter when Swiss-American astronomer Fritz Zwicky noticed that galaxies in the Coma cluster moved so quickly that they should have flung away into space. Yet, they remained gravitationally bound to the galaxy cluster by an unseen matter.
The same type of problem was observed in the 1970s by American astronomer Vera Rubin on individual spiral galaxies, where there seems to be much more matter in these galaxies to hold the stars in orbit. These discoveries have led scientists to try to piece together the puzzle using limited clues.
It is believed that dark matter constitutes 85% of the total mass of the universe. Meanwhile, normal matter, including all the stars, planets, black holes, and everything else that can be detected, only makes up the minority.
Unlike normal matter, however, dark matter does not interact with electromagnetic force, so it does absorb, reflect, or emit light. This makes it difficult to detect this elusive matter. As a matter of fact, astronomers only rely on gravitational lenses to infer the existence of dark matter and estimate how much of it is present in galaxy clusters.
In a recent study, scientists suggest that we may also be able to detect dark matter using planets.
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Signal for Dark Matter in Jovian Atmosphere
In 1997, experts discovered an interesting twist in the search for dark matter with the launch of the Cassini spacecraft with the goal of studying Saturn and its system. During the seven-year journey, the spacecraft will be sent to the target planet through gravitational slingshots from Venus, Earth, and Jupiter.
During the mission, astronomers used the Visual and Infrared Mapping Spectrometer (VIMS) to measure levels of hydrogen ions called trihydrogen cations. These particles are commonly found across the universe and are formed from the interaction of molecular hydrogen with planetary lightning, extreme ultraviolet radiation, and cosmic rays.
In the study "Search for dark matter ionization on the night side of Jupiter with Cassini," researchers Carlos Blanco and Rebecca K. Leane explored how dark matter can also produce trihydrogen cation in planetary atmospheres. Any dark matter that is captured and is consistently annihilated in the ionosphere, can produce detectable ionizing radiation.
Blanco and Leane used data from Cassini VISM system to search for dark matter ionization in the atmosphere of Jupiter. This gas giant is considered as the most efficient captor of dark matter in the Solar System.
This mission is challenged by the fact that there are a lot of active ionizing processes in the Solar System. To address this problem, the researchers looked at three-hour measurements from Jupiter's equatorial region at night.
Choosing this time meant minimum influence from solar extreme ultraviolet irradiation. For the first time, the researchers have confirmed that dark matter can indeed create ionizing radiation in planetary atmospheres. This phenomenon was found to be detectable through a smoking-gun excess of atmospheric trihydrogen cations.
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