Featured Research

from universities, journals, and other organizations

New study adds to finding of ancient life signs in Mars meteorite

Date:
November 30, 2009
Source:
NASA/Johnson Space Center
Summary:
Using more advanced analytical instruments now available, a Johnson Space Center research team has reexamined the 1996 finding that a meteorite contains strong evidence that life may have existed on ancient Mars.

Complex biomorphs appear on another Nakhla chip shown in this scanning electron microscope (SEM) frame. This image contains three basic forms: Broad smooth knife-shaped features, elongated features with rounded endcaps and transverse compartments or dividers, and donut shaped small features, each about 1 micrometer in diameter. One possibility is the donut-shaped features are derived from the compartments present in the elongated features.
Credit: NASA/David McKay

Using more advanced analytical instruments now available, a Johnson Space Center research team has reexamined the 1996 finding that a meteorite contains strong evidence that life may have existed on ancient Mars.

The new research focused on investigating alternate proposals for the creation of materials thought to be signs of ancient life found in the meteorite. The new study argues that ancient life remains the most plausible explanation for the materials and structures found in the meteorite.

In 1996, a group of scientists led by David McKay, Everett Gibson and Kathie Thomas-Keprta of NASA's Johnson Space Center (JSC) in Houston published an article in Science announcing the discovery of biogenic evidence in the ALH84001 meteorite. A newly published paper revisits that original hypothesis with new analyses. The paper, "Origin of Magnetite Nanocrystals in Martian Meteorite ALH84001," by Thomas-Keprta and coauthors Simon Clemett, McKay, Gibson and Susan Wentworth, all scientists in the Astromaterials Research and Exploration Science Directorate at JSC, is in the November issue of the journal Geochimica et Cosmochimica Acta of The Geochemical Society and The Meteoritical Society.

Magnetite crystals in ALH84001 have been a focus of debate about the possibility of life on Mars. Magnetite is an iron-bearing, magnetic mineral. On Earth, some water and soil bacteria secrete the mineral within their cells. The 1996 study suggested that some magnetite crystals associated with carbonate globules in ALH84001 are biogenic because they share many characteristics with those found in bacteria on Earth. Other scientists have argued instead that the magnetite in ALH84001 was likely caused by inorganic processes, and that those same processes can be recreated artificially in the laboratory by heating carbonates in a process known as thermal decomposition, forming magnetite identical to that found in the Mars meteorite.

In this new study, the JSC research team reassessed the leading alternative non-biologic hypothesis that heating or shock decomposition produced the magnetites. The authors argue that their new results do not support the heating hypothesis for the formation of the magnetites. They conclude that the biogenic explanation is a more viable hypothesis for the origin of the magnetites.

"In this study, we interpret our results to suggest that the in situ inorganic hypotheses are inconsistent with the data, and thus infer that the biogenic hypothesis is still a viable explanation," said lead author Thomas-Keprta, senior scientist for Barrios Technology at JSC.

"We believe that the biogenic hypothesis is stronger now than when we first proposed it 13 years ago," said Gibson, NASA senior scientist.

In addition to the new paper on ALH84001, the JSC team has published a paper that identifies shapes or morphologies in Martian meteorites that resemble known microfossil and microbial shapes in samples from Earth. These new shapes, seen with a scanning electron microscope, are termed biomorphs because of their close resemblance to known, biologically produced features on Earth. The biomorphs observed in the meteorites will be the focus of the JSC team with more detailed studies, including chemical and isotopic analyses.

"The evidence supporting the possibility of past life on Mars has been slowly building up during the past decade," said McKay, NASA chief scientist for exploration and astrobiology, JSC. "This evidence includes signs of past surface water including remains of rivers, lakes and possibly oceans, signs of current water near or at the surface, water-derived deposits of clay minerals and carbonates in old terrain, and the recent release of methane into the Martian atmosphere, a finding that may have several explanations, including the presence of microbial life, the main source of methane on Earth."

To view the two papers, imagery and associated materials on the Internet, visit: http://www.nasa.gov/centers/johnson/home/mars_meteorite.html


Story Source:

The above story is based on materials provided by NASA/Johnson Space Center. Note: Materials may be edited for content and length.


Journal References:

  1. K.L. Thomas-Keprta, S.J. Clemett, D.S. McKay, E.K. Gibson, S.J. Wentworth. Origins of magnetite nanocrystals in Martian meteorite ALH84001. Geochimica et Cosmochimica Acta, 2009; 73 (21): 6631 DOI: 10.1016/j.gca.2009.05.064
  2. David S. McKay, Kathy L. Thomas-Keprta, Simon J. Clemett, Everett K. Gibson, Jr., Lauren Spencer, Susan J. Wentworth. Life on Mars: new evidence from martian meteorites. Proc. SPIE, 2009; 7441: 744102 DOI: 10.1117/12.832317

Cite This Page:

NASA/Johnson Space Center. "New study adds to finding of ancient life signs in Mars meteorite." ScienceDaily. ScienceDaily, 30 November 2009. <www.sciencedaily.com/releases/2009/11/091130111111.htm>.
NASA/Johnson Space Center. (2009, November 30). New study adds to finding of ancient life signs in Mars meteorite. ScienceDaily. Retrieved September 19, 2014 from www.sciencedaily.com/releases/2009/11/091130111111.htm
NASA/Johnson Space Center. "New study adds to finding of ancient life signs in Mars meteorite." ScienceDaily. www.sciencedaily.com/releases/2009/11/091130111111.htm (accessed September 19, 2014).

Share This



More Space & Time News

Friday, September 19, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Boeing, SpaceX to Send Astronauts to Space Station

Boeing, SpaceX to Send Astronauts to Space Station

AFP (Sep. 17, 2014) — NASA selected Boeing and SpaceX on Tuesday to build America's next spacecraft to carry astronauts to the International Space Station (ISS) by 2017, opening the way to a new chapter in human spaceflight. Duration: 01:13 Video provided by AFP
Powered by NewsLook.com
East Coast Treated To Rare Meteor Sighting

East Coast Treated To Rare Meteor Sighting

Newsy (Sep. 16, 2014) — Numerous residents along the East Coast reported seeing a bright meteor flash through the sky Sunday night. Video provided by Newsy
Powered by NewsLook.com
Space Race Pits Bezos Vs Musk

Space Race Pits Bezos Vs Musk

Reuters - Business Video Online (Sep. 16, 2014) — Amazon CEO Jeff Bezos' startup will team up with Boeing and Lockheed to develop rocket engines as Elon Musk races to have his rockets certified. Fred Katayama reports. Video provided by Reuters
Powered by NewsLook.com
NASA Picks Boeing and SpaceX to Ferry Astronauts

NASA Picks Boeing and SpaceX to Ferry Astronauts

AP (Sep. 16, 2014) — NASA is a giant step closer to launching Americans again from U.S. soil. It has announced it has picked Boeing and SpaceX to transport astronauts to the International Space Station in the next few years. (Sept. 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