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TOPIC: Extinction
Blobrana


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RE: Extinction
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 Did exploding stars help life on Earth to thrive?

Research by a Danish physicist suggests that the explosion of massive stars - supernovae - near the Solar System has strongly influenced the development of life. Prof. Henrik Svensmark of the Technical University of Denmark (DTU) sets out his novel work in a paper in the journal Monthly Notices of the Royal Astronomical Society.
When the most massive stars exhaust their available fuel and reach the end of their lives, they explode as supernovae, tremendously powerful explosions that are briefly brighter than an entire galaxy of normal stars. The remnants of these dramatic events also release vast numbers of high-energy charged particles known as galactic cosmic rays (GCR). If a supernova is close enough to the Solar System, the enhanced GCR levels can have a direct impact on the atmosphere of the Earth.
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Ed ~ Highly dubious research. Other research on mutations levels show no effect of nearby supernovae. And we already have robust theories on the causes of fluctuations in biodiversity levels.



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Blobrana


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Research links uplifting continents to crashes in biodiversity on Earth

A mysterious cycle of booms and busts in marine biodiversity over the past 500 million years could be tied to a periodic uplifting of the worlds continents, scientists report in the latest issue of The Journal of Geology.
The researchers discovered periodic increases in the amount of the isotope strontium-87 found in marine fossils. The timing of these increases corresponds to previously discovered low points in marine biodiversity that occur in the fossil record roughly every 60 million years. Adrian Melott, professor of physics and astronomy at the University of Kansas and lead author, thinks these periodic extinctions and the increased amounts of strontium-87 are linked.
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Blobrana


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60 Myr periodicity
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Title: A ~60 Myr periodicity is common to marine-87Sr/86Sr, fossil biodiversity, and large-scale sedimentation: what does the periodicity reflect?
Authors: Adrian L. Melott, Richard K. Bambach, Kenni D. Petersen, and John M. McArthur

We find that the marine 87Sr/86Sr record shows a significant periodicity of 59.3 ± 3 Myr. The 87Sr/86Sr record is 171° ± 12° out of phase with a 62 (± 3) Myr periodicity previously reported in the record of marine-animal diversity. These periodicities are close to 58 (± 4) Myr cycles found for the number of gap-bounded sedimentary carbonate packages of North America We propose that these periodicities reflect the operation of a periodic pulse of the Earth in large-scale, Earth processes. These may be linked to mantle or plate-tectonic events, possibly uplift, which affects Earths climate and oceans, and so the geochemistry, sedimentation, and biodiversity of the marine realm.
It has frequently been suggested that large-scale geological phenomena may be the driver for large-scale evolutionary change that is revealed in the fossil record; for example, that the emplacement of large igneous-provinces may drive mass extinctions (e.g. Courtillot et al., 1996).
Possible connections between large-scale tectonic phenomena, the fossil record, and the record of marine 87Sr/86Sr (a proxy for continental weathering) have been noted before, by casual allusion (e.g. McArthur et al. 2001), minimal discussion (Prokopf 2009) discussion that lacked quantification (Halverson et al., 2007; Purdy, 2008). Here we provide a time-series analysis of an independent signal of the geological record in an attempt to reveal more about large-scale geological events as potential drivers of biodiversity change.

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Blobrana


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Title: Occurrence of potentially hazardous GRBs launched in globular clusters
Authors: Wilfried F. Domainko

Nearby, Galactic gamma-ray bursts (GRBs) may affect the terrestrial biota if their radiation is beamed towards the Earth. Compact stellar binary mergers are possible central engines of short GRBs and their rate could be boosted in globular clusters. Globular cluster typically follow well defined orbits around the galactic center. Therefore their position relative to the solar system can be calculated back in time. This fact is used to demonstrate that globular cluster - solar system encounters define possible points in time when a nearby GRB could have exploded. Additionally, potential terrestrial signatures in the geological record connected to such an event are discussed. Assuming rates of GRBs launched in globular cluster found from the redshift distribution of short burst and adopting the current globular cluster space-density around the solar system it is found that the expected minimal distance d_min for such a GRB in the last Gyr is in the range d_min ~ 1 - 3.5 kpc. From the average gamma-ray luminosity of a short GRB significant depletion of the terrestrial ozone-layer is expected if such an event explodes at a distance of ~1 kpc. In the last Gyr a few globular cluster passages are expected within a distance of d_min from the solar system and a GRB should have exploded during one of these passages. Globular cluster - solar system encounters and events of mass extinction in the history of life can be correlated to investigate the impact of a nearby GRB on the terrestrial biota. To explore such a correlation reliable globular cluster positions relative to the solar system have to be calculated for the time span of the fossil record of the last 600 Myr. The upcoming GAIA mission will be crucial to determine the possible time intervals of the occurrence of nearby GRBs launched in globular clusters.

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Blobrana


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World's oceans in 'shocking' decline

The oceans are in a worse state than previously suspected, according to an expert panel of scientists.
In a new report, they warn that ocean life is "at high risk of entering a phase of extinction of marine species unprecedented in human history".
They conclude that issues such as over-fishing, pollution and climate change are acting together in ways that have not previously been recognised.
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Blobrana


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Arabian Oryx Makes History as First Species to Be Upgraded from "Extinct in the Wild" to "Vulnerable"

The latest update to the IUCN Red List of Threatened Species includes an all-too-rare victory: The Arabian Oryx (Oryx leucoryx) has been upgraded from the Endangered category to Vulnerable.
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Blobrana


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Great Indian bustard faces extinction

One of the heaviest flying birds in the world is in danger of going extinct, conservationists are warning.
Great Indian bustards stand a metre tall and weigh up to 15kg, yet as few as 250 may now survive.
That is according to the latest edition of the IUCN Red List for Birds, which reports that the total number of threatened birds species has risen to 1253.
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Blobrana


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Exploring meteor-extinction links

Senior Research Fellow Dr Fred Jourdan of Curtin University's Applied Geology Department is looking to space to explore mass extinctions on Earth.
Born in the northern France, Dr Jourdan grew up in Gevena, near scientific research mecca CERN.
He credits an enthusiastic teacher with inspiring his passion for science, a zest apparent as he discusses his work.
Currently he has two projects on the go, both looking at major events coinciding with large extinctions. The first explores massive volcanos - some the size of WA - and the other major meteor impacts.
This latter project, Consequences of Extra-Terrestrial Impacts on the Biosphere and Geosphere, with Dr Eric Tover (UWA), recently received $180,000 in Australian Research Council (ARC) Discovery Project funding.
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Seagrasses face extinction threat

Seagrasses around the world are disappearing, with some species now threatened with extinction.
The first global survey of individual seagrass species has found that 14% are at risk of going extinct.
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Species extinction rates have been overestimated, new study claims

The most widely used methods for calculating species extinction rates are "fundamentally flawed" and overestimate extinction rates by as much as 160 percent, life scientists report May 19 in the journal Nature.
However, while the problem of species extinction caused by habitat loss is not as dire as many conservationists and scientists had believed, the global extinction crisis is real, says Stephen Hubbell, a distinguished professor of ecology and evolutionary biology at UCLA and co-author of the Nature paper.
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