To look The minor planet Pluto and Titan, Saturn’s largest moon, surprised astronomers after The James Webb Space Telescope (JWST) discovered a chemical signature on their surfaces that did not match any records recorded in the exhibition databases. The researchers believe that this is not the fault of the instrument, but the signature of a compound whose identity remains a mystery—a combination of materials that have not been studied in the laboratory, or even a compound whose chemistry has not yet been determined.
Discovery appears in a reading pending publication in the journal Astronomy & Astrophysics. Scientists identified an absorption band centered at 5.113 micrometers on Titan and Pluto—two worlds separated by billions of kilometers and with different physical conditions. The signal was seen in observations made by two different instruments on the JWST, leading the team to rule out the possibility that it was a calibration issue or some other type of technical error.
The key to the discovery lies in a technique known as spectroscopy. Each element or molecule interacts with light in a unique way, absorbing certain wavelengths and leaving a distinctive pattern, like a fingerprint. For decades, scientists have compiled large catalogs of these fascinating signatures to identify compounds such as water, methane, carbon dioxide, or ammonia on planets and moons, as well as on other bodies outside the solar system.
In this case, the comparison did not yield convincing matches. Furthermore, at this stage, detecting a chemical signature that cannot be linked to a known compound is very common. Therefore, figuring out what is happening on Titan and Pluto may be a new fundamental question for planetary science.
Researchers have already identified several possibilities. They studied the laboratory appearance of ice and organic compounds that may exist on this planet, including acetylene, benzene, ketene, and a family of molecules known as allenes. None of them exactly matches the observed signature. The most likely explanation is that it is from a known compound that exists in a physical state or a mixture that has never been studied in the laboratory, although the authors do not exclude the possibility that the signal comes from a material whose chemistry has not yet been demonstrated.
The fact that the same symbol appears in two different places makes the mystery even more mysterious. Titan has an atmosphere rich in nitrogen and methane with a surface pressure of about 1.5 bar—higher than Earth’s—with rivers and lakes of liquid methane and a temperature of about -180 degrees Celsius (–292 Fahrenheit). Pluto, on the other hand, remains an astonishing 10 times the mass (more than 150,000 times less dense); it has an ice-covered surface composed of nitrogen, methane, and carbon monoxide; and reaches temperatures close to -235 C (–391 Fahrenheit).
