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The harsh interstellar environment ought to destroy these carbon-rich molecules; experiments reveal their secret weapon.

Organic molecules called polycyclic aromatic hydrocarbons (PAHs) populate interstellar space and represent a major reservoir of carbon, an essential element for life. The smallest of these molecules mysteriously survive the harsh environment of space, and a research team has now explained how they do it [1]. In experiments in space-like conditions, the team showed that the molecules can use a process called recurrent fluorescence to shed some of the potentially destructive vibrational energy they receive from ultraviolet photons and molecular collisions. The results will help theorists model the dissemination of the building blocks of life throughout the cosmos.

PAHs form in dying stars and get ejected via supernovae into the interstellar medium. In 2021 they were detected in cold interstellar clouds (molecular clouds), and the JWST observatory has since confirmed widespread evidence for small PAHs at higher abundance than models predict. Small PAHs somehow survive ultraviolet radiation, molecular collisions, and other processes that trigger internal vibrations that can tear them apart.

A large impact could have briefly amplified the moon’s weak magnetic field, creating a momentary spike that was recorded in some lunar rocks. Scientists may have solved the mystery of why the moon shows ancient signs of magnetism although it has no magnetic field today. An impact, such as from a large asteroid, could have generated a cloud of ionized particles that briefly enveloped the moon and amplified its weak magnetic field.

Where did the moon’s magnetism go? Scientists have puzzled over this question for decades, ever since orbiting spacecraft picked up signs of a high magnetic field in lunar surface rocks. The moon itself has no inherent magnetism today.

Now, MIT scientists may have solved the mystery. They propose that a combination of an ancient, weak magnetic field and a large, plasma-generating impact may have temporarily created a strong magnetic field, concentrated on the far side of the moon.