All life on Earth is related. It all uses the same molecules. The genetic information of every organism on Earth is carried by DNA. All life is powered by adenosine triphosphate, ATP. All of our planet’s life forms require six specific elements to live: carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur. Biologists use the mnemonic CHNOPS, the first letter of the six elements.
All life on Earth also requires
water. It also requires a proper temperature range, although some extreme forms
of life can tolerate temperatures we humans can’t. In any search for
extraterrestrial life that is at all similar to life on Earth, we need to find
these chemicals and conditions.
That’s not to say life can’t be
based on other chemicals and conditions, but we might not be able to
immediately recognize such life, especially if it only exists in microbial form.
NASA searches for life on Mars.
Those scientists follow the mantra “Follow the water.” While water may be
absolutely critical, it is not the only resource we need to look for.
Earthly life could not exist
without the CHNOPS elements. Phosphorus is critical for life as we know it, but
it’s scarce in the universe. And, most of the phosphorus on Earth exists in the
form of phosphates, a chemical that is insoluble in water and unable to react
with organic molecules. Life on Earth wouldn’t be possible without other more
reactive forms of phosphorus.
It turns out that when lightning
strikes on Earth, it forms fulgurite. Fulgurite contains a mineral called schreibersite,
an alloy of iron, nickel, and phosphorus. This is a form of phosphorus that can
be utilized by organic chemicals.
Astronomers, led by Frank Postberg
of the Freie Universitat Berlin, recently announced the discovery of
organically available phosphorus in a new location, the moon Enceladus orbiting
Saturn. A few years ago, the scientific world was shocked by the discovery of
plums of water shooting off of this tiny moon. This water contained organic
molecules and spurred discussion of Enceladus as a possible home for
extraterrestrial life. In their paper, the astronomers say that Enceladus’
water plumes contain “a high availability of dissolved phosphorus, which is
thus extremely unlikely to be a limiting factor in the survival of putative
life on Enceladus.”
Saturn’s Moon Enceladus with water plumes, credit
NASA, JPL, and Cal Tech
That is science-speak for saying that one of the best hopes of finding life elsewhere in our solar system just got better.
Each month, I write an astronomy-related column piece for
the Oklahoman newspaper. After it is published there, I post that same column to my blog page.
