Organic chemicals around cool stars are studied

Primordial Earth. A steaming dish of hot chemicals from the newly-formed sun coats the planet. Meteorites rain down carrying prebiotic (life-forming) molecules and after a while, life emerges.

This is one of the foremost scenarios for the development of life on Earth. The clear question to follow then is: Do these same prebiotic molecules exist around other stars?

According to a recent NASA study, whose lead author is Hopkins physicist Ilaria Pascucci, stars cooler than our sun actually contain a different mix of chemicals and molecules.

Looking for life-somewhat-as-we-know-it in other universal locales can seem like an often rather ambiguous task. Scientists are limited not only by their methods but by what they can search for in the first place.

To make this discovery, they looked for a prebiotic molecule, hydrogen cyanide, which is a precursor of adenine, one of the DNA's four main building blocks.

The molecular makeups in question were detected by the Spitzer Space Telescope, which examined the light spectra of the disks of material (including planets) in orbit around particular stars.

Curiously, no hydrogen cyanide was detected around any of the cooler stars, although it was found around 30 percent of the medium-hot (sun-like) stars. One reason for this observation may be that hotter stars emit more ultraviolet radiation, which increases the production of hydrogen cyanide.

Planets around these cooler stars may have different prebiotic mixes, if they form life at all. Because hydrogen cyanide is so essential to life on Earth, scientists might consider it a prerequisite for life elsewhere.

However, the process or processes of developing life are still uncertain. Perhaps cooler stars may just permit life on their satellites that is not based on anything like DNA.

Why such interest in stars cooler than the Sun? Special interest has developed about one class of cooler stars, M-dwarfs, for their potential "super Earth" planets. These recently discovered planets are thought to be like very large versions of Earth in orbit around cooler stars.

Two problems now exist in having a super Earth. For one thing, it would need to be in orbit in the "habitable zone" around its star, where liquid water could exist. So far, none of them are in the right place.

Then, as this study shows, these planets do not contain hydrogen cyanide, so even if they were in the habitable zone, life may not be able to arise.

We will have to continue looking both into the earth, to unlock the secrets of life, and out to the stars, in order to find out more about the wheres and hows of life in the universe.