Three billion years ago, Earth was a very different place.
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TNA World
DNA is the building block for life on Earth. But it is a highly complex molecule, and could not have arranged itself spontaneously. What did it develop from? Astrobiologists examine possible ancestors of DNA: nucleic acids called PNA, p-RNA, and TNA.
We all know that DNA (Figure 1) makes up the building blocks for life on Earth. But DNA – deoxyribonucleic acid – is highly complex. It could not have appeared spontaneously; it must have evolved from a simpler form.
Scientists have put forth the theory that RNA – ribonucleic acid (Figure 2) – was the predecessor to DNA ...
March 12, 2001 • Posted by: Shige Abe • Report issue
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Ganymede's Liquid Past
Based on a NASA Ames Research Center press release
Long swaths of bright, flat terrain on the surface of Jupiter’s icy moon Ganymede may testify that water or slush emerged there about a billion years ago, say planetary scientists. NASA scientists have combined stereo images from NASA’s Galileo and Voyager missions to examine these provocative features on the moon.
This bright terrain, long since frozen over, lies uniformly in troughs about one kilometer (a little over a half mile) lower than Ganymede’s older, darker, cratered terrain.
Ganymede is the largest moon in the solar system and larger than the ...
March 09, 2001 • Posted by: Shige Abe • Report issue
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Some Like It Hot
Most people who visit Yellowstone National Park go there to take in the scenery and to catch a glimpse of the park’s iconic Old Faithful geyser. But not Jack Farmer. When he ventures out to Yellowstone, he goes in search of clues to what life might have been like on Earth – and Mars – some four billion years ago.
Farmer is an astrobiologist who heads the Arizona State University Lead Team of the NASA Astrobiology Institute (NAI). What fascinates him about Yellowstone are the microscopic organisms that inhabit the boiling waters of its hot springs. He refers to these ...
March 07, 2001 • Posted by: Shige Abe • Report issue
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A Shortage of Planets
At an age of about 10 billion years, globular clusters contain some of the oldest stars in the Milky Way. Scientists study these ancient, densely packed star systems to learn about the lives of stars, the formation of galaxies, and the evolution of the universe. By searching for planets in globular clusters, it is also possible to discover whether planets formed when our galaxy was relatively young.
Astronomer Ronald Gilliland of the Space Telescope Science Institute in Baltimore, Maryland, and his team searched for planets in the globular cluster 47 Tucanae, a crowded group of stars located about 15,000 ...
March 05, 2001 • Posted by: Shige Abe • Report issue
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Two Rovers in Search of a Landing Site
In the spring of 2003, NASA will launch two spacecraft on 35-million-mile journeys to Mars. Each craft will carry a small rover, equipped with a set of robotic geologic tools designed to search out mineral evidence within Martian rocks that water was once present on Earth’s neighboring planet.
The Mars Explorer Rovers, as they are tentatively dubbed, are larger and more-advanced descendants of the Sojourner rover that roamed the Martian surface in July 1997. Both MERs will arrive at the Red Planet early in 2004, but they will go to different, widely separated locations.
The question NASA is trying ...
March 02, 2001 • Posted by: Yael Kovo • Report issue
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Scientists Find Evidence of Ancient Microbial Life on Mars
(Text based on a NASA Ames Research Center Press Release)
An international team of researchers has discovered compelling evidence that the magnetite crystals in the martian meteorite ALH84001 are of biological origin.
The researchers found that the magnetite crystals embedded in the meteorite are arranged in long chains, which they say could have been formed only by once-living organisms. Their results are reported in the February 27 Proceedings of the National Academy of Sciences.
“The chains we discovered are of biological origin,” said Dr. Imre Friedmann, an NRC senior research fellow at NASA’s Ames Research Center in ...
February 28, 2001 • Posted by: Shige Abe • Report issue
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Apocalypse Then
(From Science@NASA)
New findings provide evidence that Earth’s most severe mass extinction – an event 250 million years ago that wiped out 90 percent of the life on Earth – was triggered by a collision with a comet or asteroid.
Over 90 percent of all marine species and 70 percent of land vertebrates perished as a result, according to the NASA-funded research team, led by Dr. Luann Becker of the University of Washington (UW), Seattle. The team’s findings will be published in today’s issue of the journal Science.
The collision wasn’t directly responsible for the extinction, but rather ...
February 26, 2001 • Posted by: Shige Abe • Report issue
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Squaring Off With a Robotic Serpent
Text Based on a NASA Ames Research Center Press Release
NASA engineers are developing an intelligent robot snake that may help explore other worlds and perform construction tasks in space.
The robot serpent, able to independently dig in loose extraterrestrial soil, smart enough to slither into cracks in a planet’s surface and capable of planning routes over or around obstacles, could be ready for space travel in five years, NASA engineers predict.
“The snake will provide us with flexibility and robustness in space,” said Gary Haith, lead “snakebot” engineer at NASA’s Ames Research Center located in California’s Silicon ...
February 21, 2001 • Posted by: Shige Abe • Report issue
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Carbonated Mars
(From Science@NASA)
A common substance found in ordinary classroom chalk could hold the key to a puzzle of planetary proportions: the mysterious whereabouts of water on Mars.
The brittle, white material in chalk – a form of carbonate – may seem rather ordinary, but finding carbonates on Mars would have some extraordinary implications. The discovery would provide strong evidence that liquid water once flowed on the Red Planet. Such carbonates might also harbor the fossils of ancient Martian bacteria.
Carbonates are rocks and minerals which contain a molecule made of both carbon and oxygen known as CO32-. Limestone is ...
February 14, 2001 • Posted by: Shige Abe • Report issue
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A Visit to Cupid for Valentine's Day
Around Valentine’s Day this year, the hearts of many scientists will beat a little faster.
That’s because on February 12, a spacecraft will land on an asteroid for the very first time.
For the past year, the Near Earth Asteroid Rendezvous (NEAR) Shoemaker spacecraft has been orbiting 433 Eros, a large asteroid located about 176 million kilometers (109 million miles) from Earth. Eros is the Greek name for Cupid, the familiar bringer of love from classical mythology.
The spacecraft has relayed thousands of photographs of the asteroid back to Earth, giving scientists the opportunity to pick the perfect landing spot ...
February 12, 2001 • Posted by: Shige Abe • Report issue
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Seeing Mars Through a Test Tube
By recreating the Martian surface in the laboratory, NASA scientists may have begun to answer two questions that have been plaguing scientists for years: why the Martian surface is so red, and why organic life has not yet been found there.
One answer, say the scientists, could be an important reactive oxygen molecule, called a superoxide anion, or negatively charged oxygen (O2-).
To test this hypothesis requires some way to test for hostile conditions in a laboratory. The researchers therefore first had to replicate a harsh Martian environment, but in a controlled recipe that they could sample reliably and easily ...
February 09, 2001 • Posted by: Shige Abe • Report issue
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Looking for Life, Astrobiologists Dive Deep
A team of interdisciplinary astrobiologists from NASA and other agencies is homing in on recognizing the microbial biosignatures for life, making it easier someday to identify life on other planets.
A scientific paper analyzing the team’s research results, titled “Modern Freshwater Microbialite Analogues for Ancient Dendritic Reef Structures,” was published in the journal Nature on October 5. The paper focuses on the study of mounded microbialite deposits – layers of living and non-living organisms – found at Pavilion Lake in Canada.
Microbialites are organic sedimentary mineral deposits covered by a thin layer of microbes that become entombed in the ...February 07, 2001 • Posted by: Shige Abe • Report issue
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Jovian Moons
Our moon, while celebrated in song and literature for its beauty, does not harbor life. With no atmosphere and little known water, conditions on our moon are not adequate to support life as we understand it. There are, however, a total of 61 moons orbiting the 9 planets in our solar system and some of them have atmospheres, organic molecules, water, or heat energy – the conditions necessary for life to exist.
The larger moons of Jupiter, for instance, have some of the qualities that would make life possible. These moons – Europa, Io, Callisto, and Ganymede – are called ...
February 02, 2001 • Posted by: Shige Abe • Report issue
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Scientists Find Clues That Life Began in Deep Space
Text based on a NASA Ames Research Center press release
Duplicating the harsh conditions of cold interstellar space in their laboratory, NASA scientists have created primitive cells that mimic the membranous structures found in all living things. These chemical compounds may have played a part in the origin of life.
This breakthrough by scientists at NASA Ames Research Center in California’s Silicon Valley is important because some scientists believe that the delivery – by comets, meteorites and interplanetary dust – of similar organic compounds born in interstellar space might have “kick-started” life on Earth.
“Scientists believe the molecules needed to ...
January 30, 2001 • Posted by: Shige Abe • Report issue
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Without Jupiter, Home Alone
To a biologist, the ingredients needed to form life include water, heat and organic chemicals. But some in the astrophysics and astronomy community argue that life, at least advanced life, may require an additional component: a Jupiter-sized planet in the solar neighborhood.
“A long-period Jupiter may be a prerequisite for advanced life,” said Dr. Alan Boss, a researcher in planetary formation. Boss, who works at the Carnegie Institution of Washington, is a member of the NASA Astrobiology Institute (NAI).
In our own solar system, Jupiter, with its enormous gravitational field, plays an important protective role. By deflecting comets and ...
January 29, 2001 • Posted by: Shige Abe • Report issue