Origin of Life on Earth: The Phosphate Problem

Biologists currently don’t know where or how life began on Earth, but they do have plenty of theories. They have a pretty good idea of what chemicals are required to create life. Five elements are critical for all life on our planet: carbon, hydrogen, oxygen, nitrogen, and phosphorus. Of course, many other elements come into play, but the basic structures in our cells absolutely demand these five. While all exist in our environment, they need to be highly concentrated relative to the environment in general for life to take hold. So much of the investigation into the genesis of life focuses on how to concentrate these elements.

The first, widely-accepted notion suggested that life began in tidal pools at the ocean’s edge. As tides moved out, pools of water left behind concentrated chemicals when the water evaporated. This idea held sway for many years. In the late 1970s, scientists discovered hydrothermal vents on the floor of the Pacific Ocean. These are locations where seawater seeped into Earth’s interior, became super-heated, and came back out through volcano-like vents. The hot water leached minerals out of the rock as it returned to the ocean.

This seemed to many to be even more plausible. But one puzzle still remained. Neither scenario seemed to provide the needed concentration of phosphorus. As Jonathan Toner, a University of Washington research assistant professor of Earth and space sciences described it, "For 50 years, what's called 'the phosphate problem,' has plagued studies on the origin of life.” He led a research team that studied alkaline lakes for a possible solution to the ‘phosphate problem.’ These form in low-lying areas where water collects via drainage from dry environments, often in volcanic regions, like Mono Lake in California.

Mono Lake, California. Credit U. S. Geological Survey

Typically, carbonate combines with and traps phosphorus, but in these alkaline environments, carbonate also combines with calcium which would otherwise lock-up phosphorus, too. The net result is a phosphorus concentration high enough to support life on Earth. Once again, origin-of-life theories have come back to the idea of bodies of surface water as the starting point for life on our planet.

Each month, I write an astronomy-related column piece for The Oklahoman newspaper. On the following day, I post that same column to my blog page.

This is reprinted by permission from The Oklahoman and www.newsok.com.