[meteorite-list] Ocean Asteroid Impact Could Deplete Earth's Protective Ozone Layer for Years

[Ron Baalke]

NEWS RELEASE FROM THE PLANETARY SCIENCE INSTITUTE

SENT: 
Oct. 25, 2010

FROM: 
Alan Fischer
Public Information Office
Planetary Science Institute
520-885-5648
520-622-6300
fischer at psi.edu


Ocean Asteroid Impact Could Deplete Earth's Protective 
Ozone Layer for Years

An asteroid crashing into the deep ocean could have 
dramatic worldwide environmental effects including 
depleting the Earth's protective ozone layer for 
several years, a Planetary Science Institute researcher 
has found.

This could result in a huge spike in ultraviolet radiation 
levels and hamper efforts to grow crops, as well as affect 
other life forms on Earth.

A medium-sized asteroid - between 500 meters and one km in 
diameter - smashing into Earth's deep oceans would send 
vast amounts of seawater into the air, said Elisabetta 
Pierazzo, PSI senior scientist.
 
In the past, the interest in the effects of oceanic impacts 
of medium sized asteroids have focused on the danger of 
regional tsunami, but Pierazzo's new approach, published 
recently in Earth and Planetary Science Letters, has used 
computer modeling scenarios to look at the effects such a 
strike would have on the atmospheric ozone.

Working with a team of atmospheric scientists, she looked at 
two asteroid impact scenarios: 500 meter and one km diameter 
asteroids impacting an ocean 4 km deep.

"This work represents the first attempt at combining impact 
simulations with a three-dimensional shock physics code and 
atmospheric simulations using a general circulation model 
with interactive chemistry," she said. "The results suggest 
that mid-latitude oceanic impact of one km asteroids can 
produce significant global perturbation of upper atmospheric 
chemistry, including multi-year global ozone depletion 
comparable to record ozone holes recorded in the mid 1990s."

The modeling depicted how rapidly ejected seawater, included 
as water vapor and compounds like chloride and bromide that 
hasten the destruction of the ozone, would affect atmospheric 
chemistry, said Pierazzo, the paper's lead author and project 
principal investigator.

"The removal of a significant amount of ozone in the upper 
atmosphere for an extended period of time can have important 
biological repercussions at the Earth's surface as a 
consequence of increase in surface UV-B irradiance," she said. 
"These include increased incidence of erythema (skin reddening), 
cortical cataracts, changes in plant growth and changes in 
molecular DNA."

While technology does not currently exist for diverting or 
destroying an asteroid headed for Earth, with enough lead-time 
and preparation the long-term consequences of such an impact 
can be diminished, she said.

Farmers could plant crops with higher tolerance to UV 
radiation to make up for the types that would not thrive, or 
survive, because of the breached ozone layer, she said. Food 
could be stored to prepare for a few years of reduced 
productivity, both on land and in the ocean.

The spike in UV radiation would also affect humans and animals, 
she said.

The ultraviolet index, or UVI, is a scale used to indicate the 
intensity of UV radiation at the Earth's surface, and the higher 
the number the greater chance of damage to the skin and eyes.   
A UVI of 10 or greater tends to be dangerous, resulting in 
burns to people with fair skin in a few minutes exposure, she 
said.

The highest UVI recorded on Earth has been 20, she said.

The results of a 500-meter asteroid impact could see the UVI 
jump to values above 20 for several months in the northern 
subtropics, and an impact by a 1 km asteroid would see the UVI 
rise up to 56, with levels exceeding 20 for about two years 
south of about 50 degrees latitude in both hemispheres, she said.

"A level of 56 has never been recorded before, so we are not 
sure what it is going to do," she said. "It would be produce 
major sunburn. We could stay inside to protect ourselves, but 
if you go outside during daylight hours you would burn.  You 
would have to go outside at night, after sunset, to avoid major 
damage."

The research was funded by a NASA Exobiology grant.

 
CONTACT:
Elisabetta Pierazzo
Senior Scientist  
520-547-3951
betty at psi.edu

PSI INFORMATION:
Mark V. Sykes
Director
520-622-6300
sykes at psi.edu

PSI HOMEPAGE:
http://www.psi.edu