Astronomy Cast: Exotic Life

Within our body, human beings require phosphate… one phosphorus atom and four oxygen atoms forming a molecule… for a whole lot of different stuff. Any of you who ever took high school advanced-placement biology got to memorize the ADP cycle within the body which includes phosphate as one of the major constituents of the process. One of the backbones of forming the DNA molecule, that twisted helix that defines who each of us are genetically, one of the backbones of forming that molecule is phosphate. Now the reason that people talk about making a substitution with arsenic is that if you pull out your periodic table or Google one, which is what I did, there’s a really good one at www.ptable.com… a horrible name but an excellent periodic table. When you look down the columns, the reason that the periodic table has all the strange gaps that it does… the first row only has hydrogen and helium, the next row has a limited number of things… it has two things on the left and six things on the right. That pattern of the periodic table is actually built on the pattern of orbiting electrons, so in hydrogen and helium you only have two possibilities of where to stick electrons. So you have these two items. Then with each successive movement down the list you add more possibilities for these electrons. Each column in the periodic table represents how many gaps are left in the outer-most orbital, the outer-most layer that electrons can live within. So when you’re looking at oxygen, when you’re looking at sulfur, when you’re looking at selenium, tellurium, polonium, all of these different elements that just happen to make up column 16, they all have six electrons living happily out in their outermost orbital shell and they can fit two more out there.   Now there’s been a lot of people being vocal, to say the least, about this. So the reason that you have a lot of people being vocal about this is first of all, it’s highly controversial. So, you want to prove them wrong… because that’s how science works. Someone says something new and you poke holes in what they said if you can. Now the other reason that they’re doing this is what they were feeding the bacteria that they were working with was a salt that did contain trace amounts of phosphate. So the question is were they metabolizing using this arsenic replacement molecule, or were they simply figuring out how to metabolize just enough using these trace, trace, trace amounts of phosphate. There is life that is known to exist that metabolizes phosphate at even lower levels than what existed in this particular salt. One of the things that is on the list of things that scientists are going to be doing next is figuring out how to image the DNA to actually see is the arsenic via some sort of… it’s not going to be a direct image… you don’t take an electron scanning microscope to look for arsenic… but they’re going to be looking to most likely use radioactive isotopes of arsenic to trace is the arsenic getting used to form the DNA molecules.