Featured Research

from universities, journals, and other organizations

Liquid Water At Earth's Surface 4.3 Billion Years Ago, Scientists Discover

Date:
January 11, 2001
Source:
University Of California, Los Angeles
Summary:
Strong evidence for liquid water at or near the Earth's surface 4.3 billion years ago is presented by a team of scientists in the cover story of the Jan. 11 issue of the journal Nature. The scientists — from UCLA and Curtin University of Technology in Perth, Australia — present research that pushes back our knowledge of the presence of liquid water on Earth some 400 million years.

Strong evidence for liquid water at or near the Earth's surface 4.3 billion years ago is presented by a team of scientists in the cover story of the Jan. 11 issue of the journal Nature. The scientists — from UCLA and Curtin University of Technology in Perth, Australia — present research that pushes back our knowledge of the presence of liquid water on Earth some 400 million years.

"We don't know when life began on Earth yet, but it potentially could have emerged as early as 4.3 billion years ago because we infer that all three required conditions for life existed then," said T. Mark Harrison, professor of geochemistry at UCLA, who directs UCLA's W.M. Keck Foundation Center for Isotope Geochemistry, and is a co-author of the Nature paper. "There was a source of energy: the sun; a source of raw minerals: complex organic compounds from meteorites or comets; and our inference that liquid water existed at or near the Earth's surface. Within 200 million years of the Earth's formation, all of the conditions for life on Earth appear to have been met."

Stephen J. Mojzsis, a former UCLA postdoctoral scholar in Harrison's laboratory, who is now an assistant professor of geology at the University of Colorado at Boulder and the lead author of the Nature paper, goes even further.

"The stage was set 4.3 billion years ago for life to emerge on Earth," said Mojzsis, who is also a member of the University of Colorado's NASA-funded Astrobiology Institute. "There was probably already in place an Earth with an atmosphere, an ocean, and a stable crust within about two hundred million years of the Earth's formation.

"Many geochemists believe that maintaining stable liquid water on a planetary surface that early is the most difficult of the three conditions," Mojzsis said. "The conditions for life were established very early on Earth, and this suggests that such conditions might not be uncommon in the universe. If it happened so early on, why couldn't it happen elsewhere in the universe as well? Life may not be so difficult to form when these three conditions are met."

The scientists analyzed a rock from Western Australia that was more than three billion years old with UCLA's high-resolution ion microprobe — an instrument that enables scientists to date and learn the exact composition of samples — which Mojzsis described as the "world's best instrument" for this research. The microprobe shoots a beam of ions — charged atoms — at a sample, releasing from the sample its own ions that are analyzed in a mass spectrometer. Scientists can aim the beam of ions at specific microscopic areas of a sample and analyze them without destroying the object.

The scientists learned that while the rock was deposited about three billion years ago, it contains ancient mineral grains — zircons — that were much older; two of the zircons were 4.3 billion years old, and nearly a dozen others were older than four billion years. The Earth is 4.5 billion years old. In addition, the researchers learned that the zircons contained a unique and revealing ratio of oxygen isotopes.

"We were stunned to discover a very distinctive oxygen isotopic signature in this rock — a rock that significantly predates the Earth's oxygen atmosphere — which tells us that it interacted with cold water at temperatures appropriate to the Earth's surface," Harrison said. "Many scientists did not think rocks older than two billion years could provide this information. Was there liquid water at the Earth's surface 4.3 billion years ago? We have not had any way to answer that question before until these measurements, which suggest that the answer is yes."

The telltale sign is the ratio of the very common 16O to the much rarer and heavier 18O.

"The ratio of these isotopes reveals whether water has interacted with a rock," Harrison explained. "If a rock has been to the Earth's surface and interacted with water, it will be significantly ‘heavier' and more enriched in 18O, which is precisely what we have found in these ancient zircons."

Zircons are heavy, durable minerals related to the synthetic cubic zirconium used for imitation diamonds and costume jewelry. The zircons studied in the rock are about twice the thickness of a human hair.

"These zircons tell us that they melted from an earlier rock that had been to the Earth's surface and interacted with cold water," Harrison said. "There is no other known way to account for that heavy oxygen."

The ion microprobe is the first instrument that allows high-resolution isotope analysis of inorganic and biological material only a few millionths of a meter in diameter, Harrison said.

"The microprobe is a fantastic instrument in its sensitivity, its accuracy and its versatility," Mojzsis said. "With the microprobe, we can determine the oxygen isotopic composition of individual spots within the tiny zircons, and measure with enormous precision the ages of these spots. We can determine when the zircons formed and how they formed."

Without the ion microprobe, the scientists would have been able to learn only the average age of the zircons in the rock, not the ages of the various zircons, which varied substantially, the scientists said.

Harrison and Mojzsis' colleague on the research is Robert Pidgeon, a professor of applied geology at Curtin University of Technology in Perth, Australia, who first discovered the very ancient zircons in the rock.

The research was funded by the National Science Foundation and NASA's Center for Astrobiology.

The oldest known rocks are about four billion years old, but Harrison suspects that older rocks could be found that would reveal significant information about the Earth's evolution — including perhaps the source rocks that first contained the 4.3 billion-year-old zircons — if a coordinated effort to search for ancient rocks were undertaken.

"Zircons are forever," Harrison noted.


Story Source:

The above story is based on materials provided by University Of California, Los Angeles. Note: Materials may be edited for content and length.


Cite This Page:

University Of California, Los Angeles. "Liquid Water At Earth's Surface 4.3 Billion Years Ago, Scientists Discover." ScienceDaily. ScienceDaily, 11 January 2001. <www.sciencedaily.com/releases/2001/01/010111074038.htm>.
University Of California, Los Angeles. (2001, January 11). Liquid Water At Earth's Surface 4.3 Billion Years Ago, Scientists Discover. ScienceDaily. Retrieved August 20, 2014 from www.sciencedaily.com/releases/2001/01/010111074038.htm
University Of California, Los Angeles. "Liquid Water At Earth's Surface 4.3 Billion Years Ago, Scientists Discover." ScienceDaily. www.sciencedaily.com/releases/2001/01/010111074038.htm (accessed August 20, 2014).

Share This




More Earth & Climate News

Wednesday, August 20, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Green Power Blooms as Japan Unveils 'hydrangea Solar Cell'

Green Power Blooms as Japan Unveils 'hydrangea Solar Cell'

AFP (Aug. 19, 2014) A solar cell that resembles a flower is offering a new take on green energy in Japan, where one scientist is searching for renewables that look good. Duration: 01:29 Video provided by AFP
Powered by NewsLook.com
Disquieting Times for Malaysia's 'fish Listeners'

Disquieting Times for Malaysia's 'fish Listeners'

AFP (Aug. 19, 2014) Malaysia's last "fish listeners" -- practitioners of a dying local art of listening underwater to locate their quarry -- try to keep the ancient technique alive in the face of industrial trawling and the depletion of stocks. Duration: 02:29 Video provided by AFP
Powered by NewsLook.com
Wildfire Hits California's Angeles National Forest

Wildfire Hits California's Angeles National Forest

Reuters - US Online Video (Aug. 17, 2014) A wildfire sweeps across the Angeles National Forest prompting campers to quickly leave as officials began evacuating the area -- local media. Gavino Garay reports. Video provided by Reuters
Powered by NewsLook.com
Symphony Performs at Southern Utah's Red Rocks

Symphony Performs at Southern Utah's Red Rocks

AP (Aug. 16, 2014) The Utah Symphony hopes to complement the beauty of Utah's soaring red rocks and canyons with free desert performances near Utah's national parks this weekend. (Aug. 16) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins