Defense contractor Northrop Grumman is promising the Pentagon that it'll have weapons-grade electric lasers by the end of 2008. Which means honest-to-goodness energy weapons might actually become a military reality, after decades of fruitless searching.

For the longest time, the military concentrated on developing chemical-powered lasers. They produced massively powerful laser blasts. But the noxious stuff needed to produce all that power makes the weapons all-but-impractical in a war zone. So the Defense Department shifted gears, and poured money into solid-state, electric lasers instead. Under its Joint High-Powered Solid State Laser (JHPSSL) project, these beams -- once considered too weak to do soldiers much good -- have made steady progress. Now Northrop is promising to hit what's widely considered to be the threshold for military-strength beams: 100 kilowatts. With that much energy, lasers should be able to knock mortars and rockets out of the sky.

©Northrop Grumman

A team of archaeologists claims to have discovered remnants of the legendary Khazar kingdom in southern Russia, according to a recent report. If the findings by the Russian team, reported by the French agency AFP, prove to be indeed the long-lost capital of the reputed Jewish state, they would represent one of the largest breakthroughs in Jewish archaeology.

©Unknown

Map of the Khazar kingdom and surrounding regions, including Israel

DARMSTADT, Germany - The European deep space probe Rosetta successfully completed a flyby of an asteroid millions of miles from earth, but its high resolution camera stopped shortly before the closest pass, space officials said Saturday.

Rosetta caught up with the Steins asteroid, also known as Asteroid 2867, just after 8:45 p.m. (1845 GMT) Friday in the asteroid belt between the orbits of Mars and Jupiter. The probe came within 500 miles (805 kilometers) of the asteroid - which turned out to be slightly larger than scientists expected.

A strange mix of oxygen found in a stony meteorite that exploded over Pueblito de Allende, Mexico nearly 40 years ago has puzzled scientists ever since.

©Susan Brown

Pale specks on the surface of this meteorite are among the oldest minerals in the solar system. An odd mix of oxygen atoms within these minerals has puzzled scientists for decades.

Small flecks of minerals lodged in the stone and thought to date from the beginning of the solar system have a pattern of oxygen types, or isotopes, that differs from those found in all known planetary rocks, including those from Earth, its Moon and meteorites from Mars.

Now scientists from UC San Diego and Lawrence Berkeley National Laboratory have eliminated one model proposed to explain the anomaly: the idea that light from the early Sun could have shifted the balance of oxygen isotopes in molecules that formed after it turned on. When they beamed light through carbon monoxide gas to form carbon dioxide, the balance of oxygen isotopes in the new molecules failed to shift in ways predicted by the model they report in the September 5 issue of Science.

Out of the 3 billion genetic letters that spell out the human genome, Yale scientists have found a handful that may have contributed to the evolutionary changes in human limbs that enabled us to manipulate tools and walk upright.

©Yale University

A rapidly evolving sequence from the human genome drives gene activity in the developing thumb, wrist and ankle of mouse embryos.

Results from a comparative analysis of the human, chimpanzee, rhesus macaque and other genomes reported in the journal Science suggest our evolution may have been driven not only by sequence changes in genes, but by changes in areas of the genome once thought of as "junk DNA."

Those changes activated genes in primordial thumb and big toe in a developing mouse embryo, the researchers found.

"Our study identifies a potential genetic contributor to fundamental morphological differences between humans and apes," said James Noonan, Assistant Professor of Genetics in the Yale University School of Medicine and the senior author of the study.

Astronomical instruments needed to answer crucial questions, such as the search for Earth-like planets or the way the Universe expands, have come a step closer with the first demonstration at the telescope of a new calibration system for precise spectrographs.

©ESO

Artist's impression of the laser comb developed for astronomy. Such a laser comb is necessary to act as a "ruler" for calibrating the new, extremely precise spectrographs that will be needed in the future to search for Earth-like planets or measure the expansion of the Universe.

The method uses a Nobel Prize-winning technology called a 'laser frequency comb', and is published in this week's issue of Science.

"It looks as if we are on the way to fulfil one of astronomers' dreams," says team member Theodor Hänsch, director at the Max Planck Institute for Quantum Optics (MPQ) in Germany. Hänsch, together with John Hall, was awarded the 2005 Nobel Prize in Physics for work including the frequency comb technique.

Astronomers use instruments called spectrographs to spread the light from celestial objects into its component colours, or frequencies, in the same way water droplets create a rainbow from sunlight. They can then measure the velocities of stars, galaxies and quasars, search for planets around other stars, or study the expansion of the Universe. A spectrograph must be accurately calibrated so that the frequencies of light can be correctly measured. This is similar to how we need accurate rulers to measure lengths correctly. In the present case, a laser provides a sort of ruler, for measuring colours rather than distances, with an extremely accurate and fine grid.

In a surprising reversal of conventional wisdom, a DNA-based study has revealed that the last of the woolly mammoths - which lived between 40,000 and 4,000 years ago - had roots that were exclusively North American.

©Hendrik Poinar

The last of the woolly mammoths originated in North America.

The research, which appears in the September issue of Current Biology, is expected to cause some controversy within the paleontological community.

"Scientists have always thought that because mammoths roamed such a huge territory - from Western Europe to Central North America - that North American woolly mammoths were a sideshow of no particular significance to the evolution of the species," said Hendrik Poinar, associate professor in the departments of Anthropology, and Pathology & Molecular Medicine at McMaster University.

Poinar and Régis Debruyne, a postdoctoral research fellow in Poinar's lab, spent the last three years collecting and sampling mammoths over much of their former range in Siberia and North America, extracting DNA and meticulously piecing together, comparing and overlapping hundreds of mammoth specimen using the second largest ancient DNA dataset available.

Why is it that the origins of many serious diseases remain a mystery? In considering that question, a scientist at the University of California, San Diego School of Medicine has come up with a unified molecular view of the indivisible unit of life, the cell, which may provide an answer.

©University of California - San Diego

Illustration of "molecular building blocks."

Reviewing findings from multiple disciplines, Jamey Marth, Ph.D., UC San Diego Professor of Cellular and Molecular Medicine and Investigator with the Howard Hughes Medical Institute, realized that only 68 molecular building blocks are used to construct these four fundamental components of cells: the nucleic acids (DNA and RNA), proteins, glycans and lipids. His work, which illustrates the primary composition of all cells, is published in the September issue of Nature Cell Biology.

Like the periodic table of elements, first published in 1869 by Russian chemist Dmitri Mendeleev, is to chemistry, Marth's visual metaphor offers a new framework for biologists.

This new illustration defines the basic molecular building blocks of life and currently includes 32 glycans (sugar linkages found throughout the cell) and eight kinds of lipids (which compose cell membranes) along with the more well-known 20 amino acids that are used to make proteins and the eight nucleosides that compose the nucleic acids, DNA and RNA.

"These 68 building blocks provide the structural basis for the molecular choreography that constitutes the entire life of a cell," said Marth. "And two of the four cellular components are produced by these molecular building blocks in processes that cannot be encoded by the genes. These cellular components - the glycans and lipids - may now hold the keys to uncovering the origins of many grievous diseases that continue to evade understanding."

Jerusalem - Israeli archaeologists unveiled on Wednesday a 2,100-year-old Jerusalem perimeter wall -- along with beer bottles left behind by 19th century researchers who first discovered the stone defences.

©REUTERS/Ronen Zvulun

People stand at an excavation site in Jerusalem's Old City September 3, 2008. Israeli archaeologists unveiled on Wednesday a 2,100-year-old Jerusalem perimeter wall -- along with beer bottles left behind by 19th century researchers who first discovered the stone defences. The wall, on Mount Zion at the southern edge of Jerusalem's Old City, dates back to the Second Jewish Temple, which was destroyed by the Romans in AD 70.

The wall, on Mount Zion at the southern edge of Jerusalem's Old City, dates back to the Second Jewish Temple, which was destroyed by the Romans in AD 70.

Yehiel Zelinger, who headed the excavation for the Israel Antiquities Authority, said the location of the wall indicated that Jerusalem had expanded to the south at the time, reaching its largest size in biblical times.

The 3.2-metre (10.5-foot)-high wall was not supported by any mortar or other bonding material and formed part of a 6 km (3.5-mile)-long fortification around the city, he said.

The present wall around Jerusalem's Old City is 4 km (2.5 miles) in circumference.

Physicists of the DZero experiment at the U.S. Department of Energy's Fermi National Accelerator Laboratory have discovered a new particle made of three quarks, the Omega-sub-b (Ωb).

©DZero collaboration

Once produced, the decay of the Omega-sub-b (Ωb) proceeds like fireworks. The particle travels about a millimeter before it disintegrates into two intermediate particles called J/Psi (J/ψ) and Omega-minus (Ω-). The J/Psi then promptly decays into a pair of muons. The Omega-minus baryon, on the other hand, can travel several centimeters before decaying into yet another unstable particle called a Lambda (Λ) baryon along with a long-lived particle called kaon (K). The Lambda baryon, which has no electric charge, also can travel several centimeters prior to decaying into a proton (p) and a pion (π).

The particle contains two strange quarks and a bottom quark (s-s-b). It is an exotic relative of the much more common proton and weighs about six times the proton mass.

The discovery of the doubly strange particle brings scientists a step closer to understanding exactly how quarks form matter and to completing the "periodic table of baryons." Baryons (derived from the Greek word "barys," meaning "heavy") are particles that contain three quarks, the basic building blocks of matter. The proton comprises two up quarks and a down quark (u-u-d).

Combing through almost 100 trillion collision events produced by the Tevatron particle collider at Fermilab, the DZero collaboration found 18 incidents in which the particles emerging from a proton-antiproton collision revealed the distinctive signature of the Omega-sub-b. Once produced, the Omega-sub-b travels about a millimeter before it disintegrates into lighter particles. Its decay, mediated by the weak force, occurs in about a trillionth of a second.

Theorists predicted the mass of the Omega-sub-b baryon to be in the range of 5.9 to 6.1 GeV/c2. The DZero collaboration measured its mass to be 6.165 ± 0.016 GeV/c2. The particle has the same electric charge as an electron and has spin J=1/2.