Scientists Say Cosmic Rays Created Life On Our Planet (27th April 2012)


Interesting cosmic observations from Dee, for ease of purpose the articles are posted below for your perusal.

Published on Apr 27, 2012 by

Rays of life? Fossils show that life on Earth blossomed when nearby supernovas bathed our planet in cosmic radiation

  • Rate of evolution ‘dictated’ by blasts of cosmic rays
  • Study of fossils shows life ‘bloomed’ duruing periods of intense supernova explosions
  • Long-term link between galactic events and climate

By Rob Waugh

25 April 2012

Supernova explosions when stars ‘die’ are among the most destructive events in the universe – but a new study suggests that the ‘blast wave’ from supernovae might have energised life on our planet

As our sun has ‘spun’ through the spiral arms of our galaxy, the Milky Way, it’s passed near exploding stars – being ‘bathed’ with cosmic rays which caused life to explode all over our planet.

When supernovae explode, life has prospered. ‘The evolution of life mirrors the evolution of the Galaxy,’ says Prof Henrik Svensmark of the Technical University of Denmark

An image of the Pleiades (M45), a famous star cluster about 135 million years old. This age means that any massive stars in the cluster would have exploded as supernovae when ammonites were prominent in the sea. The rate of nearby supernovae strongly influenced the diversity of such marine invertebrates

As our sun has ‘travelled’ through the Milky Way, different star clusters have caused life to blossom – explosions in the Pleiades, for instance, caused diversity in undersea creatures called ammonites, often seen in fossils.

Prof. Henrik Svensmark of the Technical University of Denmark says that when a supernova is close enough to the Solar System, galactic cosmic rays wash over the Earth.

As our sun has ‘travelled’ through the Milky Way, different star clusters have caused life to blossom – explosions in the Pleiades, for instance, caused diversity in undersea creatures called ammonites, often seen in fossils.

Prof. Svensmark looked back through 500 million years of geological and astronomical data and considered the proximity of the Sun to supernovae as it moves around our Galaxy, the Milky Way.

Prof. Svensmark was able to deduce how the rate at which supernovae exploded near the Solar System varied over time.

Comparing this with the geological record, he found that the changing frequency of nearby supernovae seems to have strongly shaped the conditions for life on Earth.

Whenever the Sun and its planets have visited regions of enhanced star formation in the Milky Way Galaxy, where exploding stars are most common, life has prospered.

Prof. Svensmark remarks in the paper, ‘The biosphere seems to contain a reflection of the sky, in that the evolution of life mirrors the evolution of the Galaxy.’

Supernova explosion: Comparing this with the geological record, he found that the changing frequency of nearby supernovae seems to have strongly shaped the conditions for life on Earth

The rate of supernova explosions correlates strongly to evolution – as judged by changes in fossils found under the ocean

In the new work, the diversity of life over the last 500 million years seems remarkably well explained by tectonics affecting the sea-level together with variations in the supernova rate, and virtually nothing else.

To obtain this result on the variety of life, or biodiversity, he followed the changing fortunes of the best-recorded fossils.

These are from invertebrate animals in the sea, such as shrimps and octopuses, or the extinct trilobites and ammonites.

They tended to be richest in their variety when continents were drifting apart and sea levels were high and less varied when the land masses gathered 250 million years ago into the supercontinent called Pangaea and the sea-level was lower. But this geophysical effect was not the whole story.

When it is removed from the record of biodiversity, what remains corresponds closely to the changing rate of nearby stellar explosions, with the variety of life being greatest when supernovae are plentiful.

A likely reason, according to Prof. Svensmark, is that the cold climate associated with high supernova rates brings a greater variety of habitats between polar and equatorial regions, while the associated stresses of life prevent the ecosystems becoming too set in their ways.

He also notices that most geological periods seem to begin and end with either an upturn or a downturn in the supernova rate.

The changes in typical species that define a period, in the transition from one to the next, could then be the result of a major change in the astrophysical environment.

Life’s prosperity, or global bioproductivity, can be tracked by the amount of carbon dioxide in the air at various times in the past as set out in the geological record.

Dr Svensmark’s research also shows that supernovae can have unpredictable – and catastrophic – effects on climate, with sea level dropping by up to 25m due to extreme cold.

This has puzzled geologists for decades.

The data also support the idea of a long-term link between cosmic rays and climate, with these climatic changes underlying the biological effects.

And compared with the temperature variations seen on short timescales as a consequence of the Sun’s influence on the influx of cosmic rays, the heating and cooling of the Earth due to cosmic rays varying with the prevailing supernova rate have been far larger.

The director of DTU Space, Prof. Eigil Friis-Christensen, comments: ‘When this enquiry into the effects of cosmic rays from supernova remnants began 16 years ago, we never imagined that it would lead us so deep into time, or into so many aspects of the Earth’s history. The connection to evolution is a culmination of this work.’

Cosmic Rays Hit Space Age High

ScienceDaily (Sep. 29, 2009) — Planning a trip to Mars? Take plenty of shielding. According to sensors on NASA’s ACE (Advanced Composition Explorer) spacecraft, galactic cosmic rays have just hit a Space Age high.

An artist’s concept of the heliosphere, a magnetic bubble that partially protects the solar system from cosmic rays. (Credit: Richard Mewaldt/Caltech)

“In 2009, cosmic ray intensities have increased 19% beyond anything we’ve seen in the past 50 years,” says Richard Mewaldt of Caltech. “The increase is significant, and it could mean we need to re-think how much radiation shielding astronauts take with them on deep-space missions.”

The cause of the surge is solar minimum, a deep lull in solar activity that began around 2007 and continues today. Researchers have long known that cosmic rays go up when solar activity goes down. Right now solar activity is as weak as it has been in modern times, setting the stage for what Mewaldt calls “a perfect storm of cosmic rays.”

“We’re experiencing the deepest solar minimum in nearly a century,” says Dean Pesnell of the Goddard Space Flight Center, “so it is no surprise that cosmic rays are at record levels for the Space Age.”

Galactic cosmic rays come from outside the solar system. They are subatomic particles–mainly protons but also some heavy nuclei–accelerated to almost light speed by distant supernova explosions. Cosmic rays cause “air showers” of secondary particles when they hit Earth’s atmosphere; they pose a health hazard to astronauts; and a single cosmic ray can disable a satellite if it hits an unlucky integrated circuit.

The sun’s magnetic field is our first line of defense against these highly-charged, energetic particles. The entire solar system from Mercury to Pluto and beyond is surrounded by a bubble of solar magnetism called “the heliosphere.” It springs from the sun’s inner magnetic dynamo and is inflated to gargantuan proportions by the solar wind. When a cosmic ray tries to enter the solar system, it must fight through the heliosphere’s outer layers; and if it makes it inside, there is a thicket of magnetic fields waiting to scatter and deflect the intruder.

“At times of low solar activity, this natural shielding is weakened, and more cosmic rays are able to reach the inner solar system,” explains Pesnell.

Mewaldt lists three aspects of the current solar minimum that are combining to create the perfect storm:

  1. The sun’s magnetic field is weak. “There has been a sharp decline in the sun’s interplanetary magnetic field (IMF) down to only 4 nanoTesla (nT) from typical values of 6 to 8 nT,” he says. “This record-low IMF undoubtedly contributes to the record-high cosmic ray fluxes.”
  2. The solar wind is flagging. “Measurements by the Ulysses spacecraft show that solar wind pressure is at a 50-year low,” he continues, “so the magnetic bubble that protects the solar system is not being inflated as much as usual.” A smaller bubble gives cosmic rays a shorter-shot into the solar system. Once a cosmic ray enters the solar system, it must “swim upstream” against the solar wind. Solar wind speeds have dropped to very low levels in 2008 and 2009, making it easier than usual for a cosmic ray to proceed.
  3. The current sheet is flattening. Imagine the sun wearing a ballerina’s skirt as wide as the entire solar system with an electrical current flowing along the wavy folds. That is the “heliospheric current sheet,” a vast transition zone where the polarity of the sun’s magnetic field changes from plus (north) to minus (south). The current sheet is important because cosmic rays tend to be guided by its folds. Lately, the current sheet has been flattening itself out, allowing cosmic rays more direct access to the inner solar system.

“If the flattening continues as it has in previous solar minima, we could see cosmic ray fluxes jump all the way to 30% above previous Space Age highs,” predicts Mewaldt.

Earth is in no great peril from the extra cosmic rays. The planet’s atmosphere and magnetic field combine to form a formidable shield against space radiation, protecting humans on the surface. Indeed, we’ve weathered storms much worse than this. Hundreds of years ago, cosmic ray fluxes were at least 200% higher than they are now. Researchers know this because when cosmic rays hit the atmosphere, they produce an isotope of beryllium, 10Be, which is preserved in polar ice. By examining ice cores, it is possible to estimate cosmic ray fluxes more than a thousand years into the past. Even with the recent surge, cosmic rays today are much weaker than they have been at times in the past millennium.

“The space era has so far experienced a time of relatively low cosmic ray activity,” says Mewaldt. “We may now be returning to levels typical of past centuries.”

NASA spacecraft will continue to monitor the situation as solar minimum unfolds. Stay tuned for updates.

http://www.sciencedaily.com/releases/2009/09/090929133244.htm

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