Just when you think life on Earth is a fragile, lonely thing comes news that one of the prime chemical building blocks of lifecalled polycyclic aromatic hydrocarbons (PAHs for short)are abundant in deep space and tough enough to survive lethal supernova explosions. PAHs are ring-shaped molecules composed of carbon and hydrogen. Researchers have found ring-shaped molecules similar to PAHs in human DNA and it looks like PAHs were the basic ingredients of all life on Earth 4.5 billion years ago. About 3,000 years ago, a massive star in the Large Magellanic Cloud exploded. In just three days time, the energy of this exploding star produced as much heat and radiation as our Sun produces in about 10 billion years. Inside the remnant of this stellar explosion, dubbed N132D, astronomers have detected vast quantities of PAH molecules. "PAHs are all around the supernova's expanding (gas) shell, according to a researcher who helped find them using NASAs Spitzer Space Telescopes infrared camera. They appear to be swept up by a shock wave of 8 million degree gas. This is causing some damage to the molecules, but many of the PAHs are surviving," he said. PAHs are one tough customer. The molecules have been found in comets, meteorites and interstellar cloudsbut this is the first evidence that PAHs can withstand a supernova blast. The fact that PAHs can survive a titanic thermonuclear explosion like a supernova is evidence that they are probably the key to building life on other planets, too. How did PAHs arrive on the ancient Earth? Comet and meteor impacts contributed greatly to the terrestrial PAH inventory. It also looks like stacks of PAH molecules form in water (seas) and thus form a kind of bridge for nucleic acids that were the forerunners of RNA and DNA. So, thanks to thermonuclear blast-hardened PAH molecules, life began here on the Earth and probably elsewhere in our vast, mysterious universe. Whats in the Sky: Is there another Earth? A good place to look is around Sunlike stars. You can see a twin of our Sun this weekend called Iota Persei; it is visible in the constellation Perseus. Look for Perseus in the northeast by around 9 p.m. Iota Persei is next to the star Mirfak, northeast of the star Algol. Iota Persei is one of the top 100 target stars for NASA's planned Terrestrial Planet Finder spacecraft.