Evidence for the prolonged presence of potentially-life-supporting, salty, acidic water on the surface of Mars claims top honors as the Breakthrough of the Year, named by Science and its publisher, AAAS, the nonprofit science society.
The findings from 2004 suggest that Mars was once a wet, warm place that could have been capable of cradling life billions of years ago, when life on Earth was getting its start.
This milestone plus nine other research advances make up Science's list of the top ten scientific developments in 2004, chosen for their profound implications for society and the advancement of science. The Top Ten list appears in the 17 December 2004 issue of the journal Science.
With the help of remote-sensing spacecraft, NASA's two hardy little robotic explorers performed the first true geologic field explorations on another planet.
The Opportunity rover discovered exposed bedrock at Eagle crater on Meridiani Planum that suggests a cyclical wet-and-dry history. The bedrock provides long-sought evidence for a prolonged wet and warm period on Mars.
On the other side of the Red Planet, the rover Spirit found evidence of shallow groundwater that may have transformed hundreds of meters of volcanic ash into soft, iron-rich rock.
Any martian life would have confronted a harsh environment dominated by salty, acidic waters that regularly dried up, but creatures capable of surviving or even thriving under such extreme conditions live here on Earth.
An international team of scientists outfitted the two identical Rovers with "eyes" that see in color, a magnifying glass, a grinding wheel for exposing fresh rock, an elemental analyzer, and two mineral-identifying instruments.
The Mars rovers are not working alone. The Thermal Emission Spectrometer on board NASA's Mars Global Surveyor provided, among other information, mineral data that helped the scientists choose Meridiani Planum as Opportunity's landing spot. New results from the European Space Agency's Mars Express orbiter point to water-weathered rocks elsewhere on Mars.
The next generation of robotic Mars explorers may attempt to bring back rock, dirt or dust samples, including hematite "blueberries" capable of preserving minute details of organisms that may have lived on Mars.
Science also salutes nine other scientific achievements of 2004. Except for the first runner up, the others are in no particular order.
The Littlest Humans: The startling discovery of a species of small human relatives in a cave on the Indonesian island of Flores suggests that modern humans and these small "hominids" shared the Earth just 18,000 years ago. The new species, Homo floresiensis, may have evolved from an earlier population of Homo erectus that was isolated on the island and then shrank to make better use of scarce resources. Or, might these fossils simply be the remains of modern humans with small heads due to a condition called "microcephaly"? The debate is sure to continue into 2005.
Human Cloning: South Korean researchers made headlines worldwide this year when they announced that they had cloned a human embryo, the first evidence that this technique could work with human cells. The researchers' intention was to derive embryonic stem cell lines that could help researchers understand complex diseases or eventually produce genetically matched replacement cells for patients.
Banner Year for Condensates: With an understanding of how to chill the two basic types of atoms into a single quantum state or "condensate" under their belts, researchers got down to probing these strange forms of matter in 2004. They learned how condensates' behavior changes as atoms grow further apart, and they created a solid condensate, complementing earlier successes with gas and liquid versions.
Hidden Genome Treasures: The stretches of "junk DNA" that lie within genomes proved this year to be far more important than previously thought. This DNA, found between genes and between a gene's protein-coding regions, turns out to be essential for helping genes turn on at the right time and in the right place.
Pulsar Pair:Astrophysicists discovered the first known pair of pulsars, spinning neutron stars that shoot out jets of radiation. Further studies of these whirling objects may provide the most stringent examination yet of Einstein's general theory of relativity.
Plant and Animal Diversity Declines: Disturbing news about the decline of species diversity rolled in from large studies this year that surveyed amphibians, butterflies, plants and birds. Not only is species richness decreasing, additional evidence suggests that climate change is altering the natural history of many different areas.
Water, Not Just on Mars: While evidence of an ancient, wet Mars grabbed the spotlight in 2004, advances in our understanding of water itself flowed freely as well. If they hold up, new results on the structure and chemical behavior of water could reshape fields from chemistry to atmospheric sciences.
Medicines for the World's Poor: "Public-private partnerships" emerged as a formidable force in 2004, affecting the way medicines are developed and delivered to developing countries. Joint ventures by foundations, rich countries, academics, pharmaceutical companies and other groups were behind several prominent initiatives this year, including a malaria vaccine trial and efforts to provide anti-HIV drugs.
Genes in a Drop of Water: In 2004, researchers hit on a new way to identify life forms too small and remote to see with the naked eye. They collected water from environments as different as the Sargasso Sea and the depths of an abandoned mine and sequenced the genes floating in it. This work has turned up new genes and genomes alike.
Science's Breakdown of the Year: Relationships between scientists and the government frayed on two continents this year as U.S. researchers accused the Bush administration of putting ideology before science and French and Italian researchers protested against budget cuts and more.
Areas to watch in 2005: This year, Science's predictions for hot fields in the upcoming year include obesity drugs, the international Haplotype Map, which should offer insights into genetic variation and human disease, and Cassini-Huygen's investigation of Saturn's moon, Titan.
The above story is based on materials provided by American Association For The Advancement Of Science. Note: Materials may be edited for content and length.
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