13 March 2000

Ultraviolet Spring

by Kate Melville

If the earth is unfortunate enough to be hit by a huge asteroid this may be just the start of the bad news. Until now scientists had thought that aside from the initial impact the major problem for survival would be the "impact winter" that follows.

However, new research from Oregon State University and the British Antarctic Survey indicates that the most deadly phase might actually start later on. What researchers are calling the "ultraviolet spring" is a combination of the residual effects of ozone depletion, acid rain and increased levels of harmful ultraviolet radiation. Your backyard fallout shelter won't offer much in the way of protection - that is if you survive the impact, tidal waves, choking dust, the impact winter, etc- in the first place.

According to Andrew Blaustein, of Oregon State University, "Scientists have pretty well documented the immediate destruction of an asteroid impact and even the impact winter which its dust cloud would create. But our study suggests that's just the beginning of the ecological disaster, not the end of it." After the initial catastrophic destruction and an impact winter, there will be widespread death of most terrestrial animals (including humans) and plants. After that what will probably happen is:

Massive acid rain caused by an atmosphere loaded with nitric oxide Acidified, the lakes and rivers with less dissolved organic carbons would allow much greater penetration of ultraviolet light.

At first the ultraviolet light would be blocked by the dust cloud kicked by the collision. During the extended winter that follows most animals would become weaker, and more vulnerable as many animals depend on exposure to ultraviolet light to keep their biological protective mechanisms operational.

When the ultraviolet spring arrives those animals and plants that had survived would have lost their resistance to ultraviolet radiation. Consequently the ultraviolet rays will penetrate far more deeply and with a greater intensity. The study concludes that this scenario would lead to ultraviolet-related DNA damage about 1,000 times higher than normal, and general ultraviolet damage to plants about 500 times higher than normal.

The problem is that ultraviolet radiation can cause mutations, cancer, and cataracts. It can kill plants or slow their growth by suppressing the photosynthesis, the very thing that forms the base of the world's food chain. During a previous asteroid hit known as the K-T event, researchers believe many of the animals were spared most of impact of an ultraviolet spring. This was just pure luck because the meteorite hit a spot on the crust of the Earth that was rich in anhydrite rocks. As a result these rocks helped produce a sulfate haze that blocked much of the ultraviolet radiation, pure luck as anhydrite rocks cover less than 1% of the Earth's surface!

So rather than worry about surviving an asteroid hit (unlikely in itself) just kick back and hope some smart astronomer sees the object first and that some mad international plan can be devised to deflect it away from the earth (it worked for Bruce Willis in Armageddon, so at least Hollywood thinks it's possible)!