Cosmic cosmetics: astronomers have found lots of nail-polish remover and sunless tanning lotion in space

It's Earth-year 6526 and you find yourself cruising interstellar space. But--drat!--your nail polish is chipped. And how will you ever restore your earthy, bronze-goddess glow so far from the tanning fight of any sunlike star? Great Hubble's ghost, what's a person to do?!

My futuristic scenario is, of course, a space-age joke, but your distress would be short-lived: Drugstore beauty products really do float around in space, sort of, and recent observations by two teams of astronomers--one led by Douglas N. Friedel, the other by Susanna L. Widicus Weaver, both at the University of Illinois at Urbana-Champaign--suggest that you won't have to comb the cosmos for such beauty aids. Nail polish remover--acetone--just what you need before you repaint your nails, is present in abundance, along with its distant chemical cousin 1,3-dihydroxyacetone (DHA), the active ingredient in sunless tanning lotion. The two chemicals have been detected before now, but the new work shows that plenty of both are suspended in the vast clouds of gas and dust that surround newly formed stars.

At first blush, the detection of large amounts of interstellar acetone and DHA may seem like nothing more than amusing curiosities. Actually, finding any complex molecule is serious science, and organic compounds such as acetone and DHA pose a special interest. Learning how much of each species is out there, as well as where they can be found, may be important for understanding the origins of life.

Astrochemists have detected more than 130 molecular species over the years, including alcohol, antifreeze, various hydrocarbons, and even sugar and salt. In spite of the numbers, finding molecules in space is very hard work.

Normally when a gas glows, the glow signals that the gas has been heated, perhaps by a nearby star, perhaps by the gravitational collapse of the cloud of gas itself. When gas particles are heated, they typically absorb energy from their surroundings, then re-emit it as light in a spectrum of distinct colors, or wavelengths, that is characteristic of the gas and identifiable by astronomers.

Unfortunately, though, interstellar nebulae, particularly the ones that harbor molecules, can include dozens or even hundreds of different kinds of gas particles. So sorting through their combined, overlapping spectra to identify one kind of molecule is a little like picking out a single fingerprint on a subway turnstile after rush hour.

As if that weren't challenging enough, the more complicated the gas particles are, in general, the more complicated the spectra they emit. The simplest spectra are emitted by atoms. Hydrogen and helium, the simplest atoms, produce clearly identifiable emission peaks in their spectra, making them relatively easy to distinguish. As soon as you stick two or more atoms together in a molecule, though, things get ugly. Unlike the rigid wooden balls and dowels of college organic chemistry sets, real molecules are more like marshmallows attached to each other with Slinkies--they flip, flop, roll, spin, squish, and vibrate, and every action leads to its own characteristic emission color.

For those reasons, the spectra of acetone and DHA are very complex indeed. The acetone molecule is made up often atoms, and DHA is made up of twelve. Their combined motions give rise to spectra with thousands of emission peaks--some isolated and narrow, others mushed together in broad bands of color. Even "color" is a bit of a misnomer; most molecules, including acetone and DHA, emit spectra at wavelengths of just a few millimeters--that is, microwaves and radio waves, invisible to the human eye.

With the recently retired, multi-antenna interferometric observatory of the Berkeley-Illinois-Maryland Association at Hat Creek, California, Friedel's team found interstellar acetone in the hot gaseous core of the Orion--KL region. The site, 1,500 fight-years from Earth, is a nursery for massive stars. Meanwhile, at the 10.4-meter single-dish Caltech Submillimeter Observatory on Manna Kea, Hawai'i, Widicus Weaver, along with Geoffrey A. Blake of Caltech, targeted another site of massive star formation. There, in another hot, gaseous core of a region called Sagittarius B2 (N-LMH), about 26,000 light-years from Earth, they identified DHA. Both clouds are rich in molecular species, but neither acetone nor DHA had been detected in the two clouds before now.

What's exciting about the discoveries is how much of the two chemicals reside in the interstellar clouds. First, each cloud is many times larger than our solar system. Moreover, the measurements suggest that trillions upon trillions of tons of acetone and DHA have collected in the two hot cores. Clearly, conditions there must be highly favorable to the formation and maintenance of the molecules. Yet such conditions are hardly typical of interstellar space.

Okay, so maybe astronauts of the distant future will have no problem sprucing up their fingernails or maintaining perfect skin tone. Acetone and DHA aren't just important grooming aids; both are basic organic molecules, and both serve as key players in many complex biochemical processes on Earth. DHA, for instance, is crucial to human metabolism.