Paper No. 10
Presentation Time: 4:10 PM


MARUYAMA, Shigenori1, AONO, Masashi1, EBISUZAKI, Toshikazu2 and DOHM, James M.3, (1)Earth-Life Science Institute, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro, Tokyo, 152-8551, Japan, (2)Riken, 2-1, Hirosawa, Wako, Saitama, 351-0198, Japan, (3)University Museum, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan,

Where on Earth is the birth place of life? This paramount question has been shrouded in mystery.

For the beginning of life, several critical conditions must be met. For example, there must be a sufficient supply of necessary elements to form the body of living organisms such as clean water, nitrogen, hydrogen, and nutrients with constant energy/material circulation. Where did such place locate on the Hadean Earth?

The answer is on the primordial continent. After the giant impact, whole Earth was melted as well as the Moon. As the planet cooled down gradually, heavy metal components sank into the core and the residual components which remained in the mantle floated on the primordial continent.

There are two critical roles of the primordial continent for life; (1) it provided a lacustrine environment and (2) it provided nutrients.

In the Hadean, chemical composition of ocean was significantly different from that of modern Earth, which was too toxic (high salinity, ultra-high acidity, and ultra-enriched in heavy metal) and impossible for life to live. Therefore, to bear life, the appearance of lakes filled with clean water is necessary. At the same time, primordial continent provided nutrients for the birth place in the Hadean. On this point, hydrothermal system at deep sea floor cannot be the birth place of life. Without a sufficient supply of nutrients from a primordial continent, the life body could not be formed, and organic radical reactions such as metabolism could not proceed.

There is no direct evidence of primordial continent on modern Earth, however it is inferable from the geologic record of the Moon. KREEP basalt, enriched in both phosphorous and potassium, which is exposed on the Moon surface had appeared on primordial continent on the Earth and must have played the key role in the origin of life.

A lake with clean water formed on the primordial continent was abundant with nutrients, which established Habitable-Trinity conditions (co-existence of the landmass, ocean, and atmosphere) under the Sun provided a suitable place for the beginning of life for the first time on the Earth.