NASA have announced a possible link between the sun’s cosmic rays and the rate of birth defects in humans.
Previous studies have suggested that cosmic rays in high doses can permanently damage human DNA, leading to birth defects.
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The first was a paper published 20 years by David Juckett and Barnett Rosenberg titled ‘Correlation of Human Longevity Oscillations with Sunspot Cycles’ in the journal Radiation Research.
They found an interesting correlation between the level of solar activity at birth and lifespan, with lower solar activity resulting in longer lifespans.
The second, by Natalia Belisheva of the Kola Science Centre, found a similar link between the solar particle events and birth defects.
‘We did a calculation of how radiation should get to the ground, and it’s far too small to explain explain the defects,’ Adrian Melott, professor of physics and astronomy at the University of Kansas told Dailymail.com.
Mellot likened the amount of radiation from cosmic events to having an X-ray taken at the dentists. He said it would require 1,000 times more radiation to cause any significant damage.
‘We have a contradiction,’ Melott said. ‘Our estimates suggest that the radiation on the ground from these solar events is very small.
‘And yet the experimental evidence suggests that something is going on that causes birth defects. We don’t understand this, which is good.
‘Something one doesn’t understand is a pointer to an interesting scientific problem.’
He added that cosmic rays may be more dangerous than thought, but there is no need to worry just yet.
‘We’ve been living all along with this,’ he said, ‘but there might mean there is more dangers from solar flares, for instance, for people living in high latitudes.’
The researchers looked at how cosmic rays from the sun create hazardous ‘secondaries’ by reacting with the Earth’s atmosphere.
‘Cosmic rays are mostly protons,’ Melott explained. ‘Basically, they are the nuclei of atoms – with all the electrons stripped off.
‘Some come from the sun. Others come from all kinds of violent events all over the universe.
‘Most of the ones that hit the Earth’s atmosphere don’t reach the ground, but they set off ‘air showers’ in which other particles are created, and some of them reach the ground.’
The air showers pose the most serious threat for the health of humans and other biology on the Earth’s surface via ‘ionizing radiation,’ according to the researcher.
‘Ionizing radiation is any radiation that can tear apart an atom or a molecule. It can affect life in many ways, causing skin cancer, birth defects and other things.
‘Normally, about one-sixth of the penetrating radiation we get down near sea level is from secondaries from cosmic rays.’
The authors looked carefully at two forms of radiation formed by solar particle events – muons and neutrons – finding that muons are the most dangerous to biology at the Earth’s surface.
‘Muons are a kind of heavy cousin of the electron,’ Melott said.
‘They’re produced in great abundance by cosmic rays and are responsible for most of the radiation we get on the ground from cosmic rays.
Of particular interest to the authors was a massive dose of solar radiation around the years 773-776 A.D.
‘Carbon-14 evidence was found in tree rings in 2012 that suggests a big radiation dose came down around 775, suggesting a huge solar particle event, at least 10 times larger than any in modern times,’ Melott said.
‘Our calculations suggest that even this was mostly harmless, but maybe there is something wrong with our assumptions.
‘We used ordinary understandings of how muons may cause damage, but perhaps there is some new physics here which makes the muons more dangerous.’
The researcher said the next step in the investigation should be honing an understanding of how much exposure to muons DNA can withstand.
‘In calculating the effect of muons, we used standard assumptions about what the effect of muons should be,’ Melott said.
‘Their physics is pretty simple, just that of an electron with a lot of mass. But no one has ever actually done much experimentation to measure the effect of muons on DNA, because under normal conditions they are not a dominant player.
‘They are not important, for example, in nuclear reactor accidents. We would like to put some synthetic DNA in a muon beam and actually measure the effect.’