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International Year of Chemistry

Chemistry is one of the main threads that tie together the grand tapestry of space exploration. Obviously, chemicals are, literally, the fuel that put our satellites into orbit around earth, and send our spacecraft to other planets. But chemistry also tells us the composition (and thus history) of stars, planets and moons, both in our Solar System, and far beyond. It also is playing a key role in the search for life.

It is our detailed understanding of chemical structures and the arrangement of electrons around atoms that allow us to detect molecules from orbit, both on Earth and other planets. For example, we can measure molecules like CO2 in our own atmosphere, frozen as dry ice in the polar cap on Mars, on icy moons of Saturn, and in the space between the stars. This technique, called spectroscopy, allows us to see something like a finger print of molecules and the atoms of which they are composed. Sometimes we are looking at visible light, such as the colors of stars which indicate temperature, age, and the presence of metal ions. But often we are looking at the many other wavelengths of the electromagnetic spectrum, which are "colors" of light not visible to the human eye. For example, while the Hubble images are mostly in visible light, the Spitzer Space Telescope sees the universe in the infrared, Galex in the Ultraviolet, Chandra in X-rays, etc.

This means that we can confidently identify elements in stars, ices and minerals on the surfaces of other planets (moons, etc.) and molecules light years away, floating in space. We can learn more than just what is out there: the speed of the rotation of the molecule is a thermometer that can tell us the temperature at a distance, and the type of ion (e.g., atoms or molecules with electrons stripped off) are a measure of how harsh is the radiation near distant stars.

Life is made of molecules, so chemistry is central to the search for life on other planets. We don't expect to be lucky enough to see a whale breaching in the oceans of Europa, its far more likely that when one of our probes detects life elsewhere it will be remains of microbes that died out long ago or live beneath the surface. In other words our first indications of life elsewhere in our Solar System will probably be chemistry. We call these molecules left over from life 'biomarkers' and much of our search strategy relies on developing chemistry to find them.

It turns out that finding biomarkers may be much more difficult than you might imagine, for at least two reasons. First, it turns out that the universe is filled with carbon compounds, some of which look quite like those in us, e.g., meteorites have been shown to contain amino acids, sugars, and nucleo bases. Second, we have no idea what alien chemistry might be like; our sophisticated biotechnology methods, which are specific to our biochemistry, may be blind to alien life.

Thus, from detecting molecules from Earth's atmosphere to other galaxies, to the search for life, chemistry is a unifying theme in NASA science.