The … organic materials in [some] meteorites probably originally formed in the interstellar medium and/or the solar protoplanetary disk, but was subsequently modified in the meteorites’ asteroidal parent bodies. … At least some molecules of prebiotic importance formed during the alteration.
Amino acids are the building blocks of life as we know it. They can be formed from abiotic (non-biological) chemical reactions (in a jar with electricity for example). It’s been known for a while that amino acids can be found on comets and asteroids, but now this fascinating article suggests that a lot of the chemical reactions that created these precursors to life happened on the asteroids themselves. Then when the asteroids bombarded the Earth, the seeds of life were delivered. More details here.
Leonid meteor shower seen from orbit. Image credit: BMDO/APL via NASA JPL.
This, of course, is just one of several hypotheses about the origin of life on Earth: livescience.com outlines seven.
This video from NASA (via physorg.com) includes a nice little section showing the movement of charged particles (cosmic rays) through the Sun’s magnetic field. What’s really neat, is that the Voyager spacecraft (now 33 years old) have discovered magnetic bubbles at the edge of the solar system that make the particles dance a little. It’s a wonderful application of the basic principles of electricity and magnetism.
Comet colliding with the Sun coincides with a coronal mass ejection. Image from the NASA SOHO Observatory.
SOHO scientists think that coronal mass ejection that happens right after the comet hits the Sun was probably not caused by the collision. But it looks really cool.
SETI has been forced to put its Allen Telescope Array into hibernation due to lack of funding. Its a sad day for exploration of the cosmos. They’re asking for help from the public to keep going.
Expanding globe of debris from the explosion of Tycho's Star. Tycho Brahe observed the star as it went supernova about 540 years ago. The red is the debris, the stardust, created by the explosion. Image from NASA.
We could have been talking about the nuclear meltdowns in Japan, but I’m not sure. Our conversations tend to wander. I remember trying to explain where the carbon atoms, that are so essential for life, came from. It’s been a while since we saw this topic, so I figured it wouldn’t hurt to go it over again. And then I found this wonderful image of the Tycho supernova from the Chandra space telescope. Supernovas are where the heaviest atoms are formed.
In the beginning … the big bang created just the smallest elements, hydrogen and helium. But even these tiny things have gravity, so they pull each other together until there’s so much stuff that the pressure at the center of the clump is enough to fuse hydrogen atoms together.
Now fusion is easy to confuse with chemical bonding that occurs around us every day. After all, the hydrogen in the atmosphere is usually in the form of H2, which is two hydrogen atoms bonding together by shared electrons.
With fusion, on the other hand, the single protons that make up the nuclei of the hydrogen atoms are pushed together to create a bigger atom, helium. I say pushed together, because it takes a lot of pressure to fuse atomic nuclei. And it also releases a lot of energy. Notice all that heat and radiation that comes from the Sun? All that energy was created by the fusion of hydrogen atoms; the smallest element, hydrogen, fuels the stars.
Fusion of two hydrogen atoms to create helium, compared the chemical bonding of hydrogen atoms to produce hydrogen gas (H2). The nutrons are left out for clarity.
The huge amounts of energy released by fusion makes fusion power one of the holy grails of nuclear energy research. If we were able to create and control self-sustaining fusion reactions, just like what happens in the Sun, we would have a source of tremendous energy. There is a lot of research in this area. Some people have figured out how to build fusion reactors in their basements, but these use a lot more energy than they produce so they’re not very useful as a power plant (Barth, 2010). The ITER reactor, currently being built in France, aims to be the first to produce more electricity than it uses.
Now back to the stars. Hydrogen atoms fuse to form helium, but it takes a lot more pressure to create larger atoms: carbon has six protons, nitrogen seven, and oxygen eight. These elements are essential for life (as we know it). The only time stellar forces are great enough to produce these are when stars explode; an exploding star is said to have gone nova. Bigger atoms, like iron (26 protons), gold (79 protons), and uranium (92 protons) need even greater forces, forces that only occur when the largest stars go supernova.
DNA. (from Wikipedia)
So if these elements are only produced in novae and supernovae, how did they get to Earth? How did they get into your DNA?
Well when stars explode, a lot of these newly formed elements are blasted off into space. It’s a sort of cosmic dust. We could even call it stardust. It’s matter, just like the hydrogen and helium from the big bang, only bigger, which means they have more mass, which means they have more gravity.
Formation of the solar system (model).
The gravity pulls the stardust together with the hydrogen and helium sill floating around in space (there’s a lot of it), to form new stars, and, now that there are the larger elements to create them, rocks, asteroids, and planets.
So, if you think about it, some stars needed to have been formed, lived their lives (which consists of fusing hydrogen atoms until they run out), and exploded to create the matter that makes up the planets in our solar system and the calcium in our bones, the sodium in our blood, and the carbon in our DNA.
Notes:
1. Lots of information about Tycho’s Star on SolStation.com.
Last Wednesday’s lunar eclipse was nicely captured in the stop-motion video below. What a wonderful way to celebrate getting past the longest night of the year. And, because the question does come up, we’re seeing the shadow of the Earth cross over the moon.
This nighttime photograph of the Nile River and its delta from the International Space Station beautifully illustrate the importance of water for life and civilization. The city of Cairo is at the neck of the delta; the brighter spot where the distributaries diverge.
Spaceflight Now has other really cool photos. Bad Astronomy has an interesting post on the logistics of this particular photo, while Heather Pringle has a very interesting post on how the desert may have aided the ancient Egyptian’s civilization.
