Science & Technology
The rise and diversification of shelled invertebrate life in the early Phanerozoic eon occurred in two major stages. During the first stage (termed as the Cambrian explosion), a large number of new phyla appeared over a short time interval approx540 Myr ago. Biodiversity at the family, genus and species level, however, remained low until the second stage marked by the Great Ordovician Biodiversification Event in the Middle Ordovician period.[1, 2, 3]
The terrestrial and lunar cratering rate is often assumed to have been nearly constant over the past 3 Gyr. Different lines of evidence, however, suggest that the impact flux from kilometre-sized bodies increased by at least a factor of two over the long-term average during the past approx100 Myr.
Very large collisions in the asteroid belt could lead temporarily to a substantial increase in the rate of impacts of meteorites on Earth.
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| ©Unknown |
| Shockwave travelling through galaxy cluster |
ESA's orbiting gamma-ray observatory, Integral, has made the first unambiguous discovery of highly energetic X-rays coming from a galaxy cluster. The find has shown the cluster to be a giant particle accelerator.
As Egyptian mummies go, Asru is a major celebrity. During her life in the 8th century B.C., she was known for her singing at the temple of Amun in Karnak; now she's famous for her medical problems. Forensic studies have revealed that although Asru lived into her 60s, she was not a well woman. She had furred-up arteries, desert lung (pneumoconiosis) caused by breathing in sand, osteoarthritis, a slipped disc, periodontal disease and possibly diabetes, as well as parasitic worms in her intestine and bladder. Her last years must have been full of pain and suffering. After all, what could her doctor do to help? Say a few prayers and recite a spell or two?
Organic molecules - in the form of methane - have been detected on a planet outside our solar system for the first time. The giant planet lies too close to its parent star for the methane to signal life, but the detection offers hope that astronomers will one day be able to analyse the atmospheres of Earth-like worlds.
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| ©Christophe Carreau/ESA |
| The giant planet HD 189733b is too hot for its methane and water vapour to signal life |
June is a time for beach parties and barbecues. It is a time for wildflowers and warm breezes and slow summer evenings. It is a time when our sun-orbiting planet cuts across a trail of cosmic debris, scattered by a monster comet, that one fine day may visit a holocaust upon us.
So says astrophysicist Victor Clube of Oxford University. He's been studying the Taurids--a meteor shower that strikes Earth each year in late June and again in November. The Taurids are not nearly as spectacular as, say, the Perseids of August; in June they're not even visible, because they approach from the dayside of the planet. But Clube and his co-workers think the Taurids are underrated. The meteor stream, they say, includes rocks so large--as much as a mile across--that to see one up close would be to lose a city, a continent, or more.
So says astrophysicist Victor Clube of Oxford University. He's been studying the Taurids--a meteor shower that strikes Earth each year in late June and again in November. The Taurids are not nearly as spectacular as, say, the Perseids of August; in June they're not even visible, because they approach from the dayside of the planet. But Clube and his co-workers think the Taurids are underrated. The meteor stream, they say, includes rocks so large--as much as a mile across--that to see one up close would be to lose a city, a continent, or more.
© David Willacy/EyeEm/Getty Images
Not long after the telescope was invented at the beginning of the 17th century, astronomers came to realise that the Moon, our only natural satellite, was not as dynamic a world as the Earth. The dark lunar tracts which early astronomers had somewhat optimistically called "maria" (seas) turned out to be nothing more than deceptively smooth plains of solidified lava. Much to astronomers' disappointment it became apparent that there were no appreciable expanses of water, though the new romantic marine nomenclature was retained, regardless - names like Mare Crisium (the Sea of Crises) and Oceanus Procellarum (the Ocean of Storms) were given in a vain attempt to grant the Moon an air of mystery and excitement [1].
In reality, the Moon's surface appeared solid and unchanging. The Moon possessed no appreciable atmosphere and there were no detectable signs of lunar life; the Church breathed a sigh of relief, having been spared the embarrassment of attempting to explain why the book of Genesis forgot to mention that our sister planet was teeming with the products of DNA.
It is unlikely the dinosaurs perished in a global firestorm triggered by the asteroid strike on Earth 65 million years ago, scientists have claimed.
A popular theory suggests the impact, which was centred on Chicxulub in Mexico, generated enough energy to set off a raging worldwide inferno.
But a new study shows rocks laid down at the time contain little charcoal - a possible tell-tale record of fires.
The researchers have published details of their work in the journal Geology.
The wildfires theory had grown up from previous research. One study had even found evidence of soot in rocks from around the Earth dating to the time of the impact.
A popular theory suggests the impact, which was centred on Chicxulub in Mexico, generated enough energy to set off a raging worldwide inferno.
But a new study shows rocks laid down at the time contain little charcoal - a possible tell-tale record of fires.
The researchers have published details of their work in the journal Geology.
The wildfires theory had grown up from previous research. One study had even found evidence of soot in rocks from around the Earth dating to the time of the impact.
More confusion at the k-t boundary
Just a few years ago, many scientists, especially physicists and astronomers, considered the Book of Science to be closed in the matter of what happened at the Cretaceous-Tertiary (K-T) boundary, 65 million years ago, and why the dinosaurs met their end. It was declared, rather imperiously, that a large asteroid had impacted the earth, causing much physical and biological devastation. Many scientific papers are still being written on this singular period in the earth's history, and the situation is no longer so clear-cut. We select for brief review four papers, each with a different perspective.
Occurrence of stishovite. Stishovite, a dense phase of silica, is widely accepted as an indicator of terrestrial impact events. It is not found at volcanic sites. Now, J.F. McHone et al report its existence at the K-T boundary, at Raton, New Mexico. (McHone, John F., et al; "Stishovite at the CretaceousTertiary Boundary, Raton, New Mexico," Science, 243:1182, 1989.) A plus for the pro-impact side.
Just a few years ago, many scientists, especially physicists and astronomers, considered the Book of Science to be closed in the matter of what happened at the Cretaceous-Tertiary (K-T) boundary, 65 million years ago, and why the dinosaurs met their end. It was declared, rather imperiously, that a large asteroid had impacted the earth, causing much physical and biological devastation. Many scientific papers are still being written on this singular period in the earth's history, and the situation is no longer so clear-cut. We select for brief review four papers, each with a different perspective.
Occurrence of stishovite. Stishovite, a dense phase of silica, is widely accepted as an indicator of terrestrial impact events. It is not found at volcanic sites. Now, J.F. McHone et al report its existence at the K-T boundary, at Raton, New Mexico. (McHone, John F., et al; "Stishovite at the CretaceousTertiary Boundary, Raton, New Mexico," Science, 243:1182, 1989.) A plus for the pro-impact side.
Comment: What they didn't consider is multiple smaller impacts as well as a larger one off Yucatan, AND overhead cometary fragment explosions.