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

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Tue, 26 Oct 2010 09:37:38 -0700 (PDT)
Message-ID: <201010261637.o9QGbcBe006775_at_zagami.jpl.nasa.gov>

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
Received on Tue 26 Oct 2010 12:37:38 PM PDT