Astronomy Question: Water In Space?

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Jennifer asks:

“Dear Astronomer,
What type of water is in space? Is it fresh water or salt water?”

Jennifer,
You’ve asked a very interesting question, one I’m happy to answer!

With Hydrogen and Helium being the two most abundant elements in our Universe, it’s no surprise that many gas-filled regions of interstellar space are for the most part, Hydrogen. If a cloud of dust and gas is cool enough to form molecules, we refer to it as a Molecular Cloud. Molecular Clouds are often “enriched” by neighboring supernova explosions which add elements heavier than Hydrogen and Helium to the mix.

Astronomers actually study molecular clouds by looking for the chemical signature of Carbon Monoxide ( CO ) since molecular Hydrogen ( H₂ ) is difficult to detect with radio and infra-red telescopes.

Of course, H₂ and CO aren’t the only molecules found in Molecular Clouds. With Oxygen being the third most common element in our galaxy after Hydrogen and Helium, the chances of H₂ combining with Oxygen to form water ( H₂O ) is pretty reasonable.

The water detected in interstellar space isn’t “salt” water like you’d find in our oceans, but it’s definitely not “pure” water either. Essentially, it’s not so much of a cloud of water with other “stuff” in it, but more a giant cloud of Hydrogen and Helium with water, Carbon Monoxide, dust, and other “stuff” in trace (but detectable) amounts. It’s kind of like asking if the water in soda is “pure” water.

Interestingly enough, astronomers have detected the chemical signatures of numerous molecules in interstellar space – not just molecular Hydrogen, Carbon Monoxide and water. Given the abundances of Hydrogen, Carbon, Oxygen, and Nitrogen in interstellar space, numerous organic compounds (those that contain carbon) have been detected.

In fact, astronomers have found over a hundred different chemical compounds in interstellar space. Some examples are: Ethylene Glycol, (CH₂OH)₂, the main ingredient in automotive anti-freeze; Ammonia, (NH₃), commonly found in glass cleaner, comets, and our “Ice Giant” planets; Acetic Acid; (CH₃COOH), commonly known as “Vinegar”; and even Glycine, (H₂NH₂CCOOH), an important Amino Acid.

Adding two more elements, Phosphorus and Sulphur, gives what astrobiologists call the CHNOPS molecules. Widely regarded as the six most important elements to life, Carbon, Hydrogen, Nitrogen, Oxygen, Phosphours, and Sulphur are found in nearly all biological molecules found on Earth.

With water and many other “organic” compounds detected in interstellar space, astronomers and astrobiologists are working diligently to better understand how life may have started here on Earth, or elsewhere in our galaxy (and beyond).

If you’d like to learn more about water and ice in Molecular Clouds, you may find this paper an interesting read:
Water, O2 and Ice in Molecular Clouds – Hollenbach et al.

Ray Sanders is a Sci-Fi geek, astronomer and blogger. Currently researching variable stars at Arizona State University, he writes for Universe Today, The Planetary Society blog, and his own blog, Dear Astronomer

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