Category Archives: life

We Began in the Stars

And We’ll Get Back There Again

For all you non-chemists in the crowd, did you know that life on Earth began with a sort of “starter yeast” of carbon-bearing compounds and other species of molecules that came from space? It’s true.

Naturally occurring ones Interstellar chemical labs contributed the iron that flows in our blood, the calcium that makes up our bones and the carbon-based molecules that make US up. And all that stuff came from stars that lived and died long ago. In the dying, they contributed elements built up over eons of time in stellar cores and atmospheres. Eventually those elements found their way to Earth, and into other chemical stewpots.

In a sense we are really the ashes of old stars, brought to life through massive and eons-long chemistry experiments. We began in stars like the ones that died to produce the Helix Nebula (left, a planetary nebula formed when a star like the Sun died) or the progenitor star that created the Crab Nebula (right) blew up more than 7,000 years ago. Near these two objects, clouds of gas and dust are scattering the chemical precursors of life. Someday perhaps they’ll combine to create new life forms.

Some 5 billion years from NOW, our Sun will start to expand and engulf the inner planets. That means that Earth (and by extension) all life upon it, will be vaporized; in essence, returned to the gas and dust from which we came. All that we were, plus all that the Sun will exhale in its dying days, will rush out to space to provide fodder for yet MORE new life, should there be places where it can form. So, while I’m not a religious person, I do find it interesting that in an astronomical sense, we are truly ashes to ashes, and dust to dust. We’ve come from space and we’ll be headed back, one way or another.

It’s Raining Primordial Soup

and the Meteorite You Rode in On

A few entries back I talked about the symposium about life in the universe that I attended last week. One of the talks we heard was about the existence of minerals and molecules in space that are the precursors to the building blocks of life. These are things like amino acids, which are pivotal in the soup of life.

Image:NWA869Meteorite.jpgWell, news comes today that confirms the the idea that meteorites are very rich sources of amino acids. Given that meteorites rain down on Earth all the time (and have done so throughout our planet’s history, it’s pretty much a given that they were generous donors to the “primordial soup” from which life on Earth sprang a few billion years ago. Scientists at the Carnegie Institution of Washington have discovered high concentrations of amino acids in two meteorites; those levels are ten times higher than other previous measurements. (For those of you who’d like to see the science results, the scientists involved have uploaded a paper for your reading pleasure.)

Amino acids are the backbones of proteins, which themselves are the “stuff” of which life is made. That’s a very simplified version of the larger biochemical story. Essentially, you have to have proteins to get life, and while some amino acids undoubtedly simmered from the stew of stuff available on early Earth, it’s plausible to assume that some of them rode in from space on meteorites. Specifically, a type of meteorite known as CR Chondrite , which contain some of the oldest and most primitive organic materials dating back to the time of our solar system’s formation. (The image at left is a sample of the NWA 869 meteorite, which is a chondrite of a similar type to a CH.)

We’ve long known that comets, which come from the Oort Cloud and have peppered Earth throughout its history, also carry organics and have long been thought of as carriers of such materials. Finding amino acids that contributed to Earth’s “soup of life” in meteorites is another step toward understanding the conditions and materials that formed the solar system