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Comet C/2013 US10 Catalina shows off a compact green coma and two tails
in this photo taken this morning (Nov. 22, 2015) at dawn from Arizona.
The green color comes from carbon compounds fluorescing in UV sunlight.
Credit: Chris Schur Amateur astronomer Chris
Schur of Arizona had only five minutes to observe and photograph Comet
Catalina this morning before twilight got the better of the night. In
that brief time, he secured two beautiful images and made a quick
observation through his 80mm refractor. He writes:
"Very
difficult observation on this one. (I observed) it visually with the
35mm Panoptic ocular. It was a round, slightly condensed object with no
sign of the twin tails that show up in the images. After five minutes,
we lost it visually as it was 2° degrees up in bright twilight. Images
show it for a longer time and a beautiful emerald green head with two
tails forming a Y shaped fan."
North is up and east to the left in these two photos of the comet made
by Dr. D.T. Durig at 6:23 a.m. EST on Nov. 21st from Cordell-Lorenz
Observatory in Sewanee, Tenn. He estimated the coma diameter at ~2 arc
minutes with a tail at least …
Schur estimated the comet's brightness at around magnitude +6. What appears to be the dust tail
extends to the lower right (southeast) with a narrower ion tail
pointing north. With its twin tails, I'm reminded of a soaring eagle or
perhaps a turkey vulture rocking back and forth on its wings. While they
scavenge for food, Catalina soaks up sunlight.
I also headed out
before dawn for a look. After a failed attempt to spot the new visitor
on Saturday, I headed down to the Lake Superior shoreline at 5:30 a.m.
today and waited until the comet rose above the murk. Using 7×50
binoculars in a similar narrow observing window, I could barely detect
it as a small, fuzzy spot 2.5° south of 4th magnitude Lambda Virginis at
5:50 a.m. 10 minutes after the start of astronomical twilight. The
camera did better!
Earth
is passing through a stream of gravelly debris from Comet Encke, source
of the annual Taurid meteor shower. Meteoroids the size of pebbles, and
larger, are disintegrating as they hit our planet's atmosphere at 30 up
to 90 km/s.
Earth runs unto the debris zone of Comet Encke every
year around this time. Usually, the encounter produces a minor meteor
shower, but 2015 is different. The Canadian Meteor Orbit Radar (CMOR)
is seeing stronger Taurid activity than any of the last few years.
Bright
fireballs are coming from a "swarm" of gravelly meteoroids that weaves
in and out of Comet Encke's dusty debris zone. In some years, Earth hits
the swarm; in other years it misses.
2015 appears to be a hit. http://spaceweather.com/
Since
the discovery of the Antarctic ozone hole, scientists, policymakers,
and the public have wondered whether we might someday see a similarly
extreme depletion of ozone over the Arctic.
But a new MIT study
finds some cause for optimism: Ozone levels in the Arctic haven't yet
sunk to the extreme lows seen in Antarctica, in part because
international efforts to limit ozone-depleting chemicals have been
successful.
"While there is certainly some depletion of Arctic
ozone, the extremes of Antarctica so far are very different from what we
find in the Arctic, even in the coldest years," says Susan Solomon, the
Ellen Swallow Richards Professor of Atmospheric Chemistry and Climate
Science at MIT, and lead author of a paper published this week in the
Proceedings of the National Academy of Sciences.
Frigid
temperatures can spur ozone loss because they create prime conditions
for the formation of polar stratospheric clouds. When sunlight hits
these clouds, it sparks a reaction between chlorine from
chlorofluorocarbons (CFCs), human-made chemicals once used for
refrigerants, foam blowing, and other applications - ultimately
destroying ozone. A success story of science and policy
After the ozone-attacking properties of CFCs were discovered in the
1980s, countries across the world agreed to phase out their use as part
of the 1987 Montreal Protocol treaty. While CFCs are no longer in use,
those emitted years ago remain in the atmosphere.
An aerial view of clouds over a mountain range in Greenland.
Courtesy of Michael Studinger/NASA Earth Observatory
Full Screen
Courtesy of Michael Studinger/NASA Earth Observatory
.
An Arctic ozone hole? Not quite
MIT researchers find that the extremes in Antarctic ozone holes have not been matched in the Arctic.
Audrey Resutek | Joint Program on the Science and Policy of Global Change
April 14, 2014
Since
the discovery of the Antarctic ozone hole, scientists, policymakers,
and the public have wondered whether we might someday see a similarly
extreme depletion of ozone over the Arctic.
But a new MIT study
finds some cause for optimism: Ozone levels in the Arctic haven’t yet
sunk to the extreme lows seen in Antarctica, in part because
international efforts to limit ozone-depleting chemicals have been
successful.
“While there is certainly some depletion of Arctic
ozone, the extremes of Antarctica so far are very different from what we
find in the Arctic, even in the coldest years,” says Susan Solomon, the
Ellen Swallow Richards Professor of Atmospheric Chemistry and Climate
Science at MIT, and lead author of a paper published this week in the Proceedings of the National Academy of Sciences.
Frigid
temperatures can spur ozone loss because they create prime conditions
for the formation of polar stratospheric clouds. When sunlight hits
these clouds, it sparks a reaction between chlorine from
chlorofluorocarbons (CFCs), human-made chemicals once used for
refrigerants, foam blowing, and other applications — ultimately
destroying ozone. 'A success story of science and policy'
After
the ozone-attacking properties of CFCs were discovered in the 1980s,
countries across the world agreed to phase out their use as part of the
1987 Montreal Protocol treaty. While CFCs are no longer in use, those
emitted years ago remain in the atmosphere. As a result, atmospheric
concentrations have peaked and are now slowly declining, but it will be
several decades before CFCs are totally eliminated from the environment —
meaning there is still some risk of ozone depletion caused by CFCs.
by Maria-Jose Vinas for NASA's Earth Science NewsGreenbelt MD (SPX) Mar 13, 2013
Maps
of ozone concentrations over the Arctic come from the Ozone Monitoring
Instrument (OMI) on NASA's Aura satellite. The left image shows March
19, 2010, and the right shows the same date in 2011. March 2010 had
relatively high ozone, while March 2011 has low levels. Credit:
NASA/Goddard.
A
combination of extreme cold temperatures, man-made chemicals and a
stagnant atmosphere were behind what became known as the Arctic ozone
hole of 2011, a new NASA study finds. Even when both poles of the planet
undergo ozone losses during the winter, the Arctic's ozone depletion
tends to be milder and shorter-lived than the Antarctic's.
This is
because the three key ingredients needed for ozone-destroying chemical
reactions -chlorine from man-made chlorofluorocarbons (CFCs), frigid
temperatures and sunlight- are not usually present in the Arctic at the
same time: the northernmost latitudes are generally not cold enough when
the sun reappears in the sky in early spring. Still, in 2011, ozone
concentrations in the Arctic atmosphere were about 20 percent lower than
its late winter average.
The new study shows that, while chlorine
in the Arctic stratosphere was the ultimate culprit of the severe ozone
loss of winter of 2011, unusually cold and persistent temperatures also
spurred ozone destruction. Furthermore, uncommon atmospheric conditions
blocked wind-driven transport of ozone from the tropics, halting the
seasonal ozone resupply until April.
"You can safely say that 2011
was very atypical: In over 30 years of satellite records, we hadn't
seen any time where it was this cold for this long," said Susan E.
Strahan, an atmospheric scientist at NASA Goddard Space Flight Center in
Greenbelt, Md., and main author of the new paper, which was recently
published in the Journal of Geophysical Research-Atmospheres.
"Arctic
ozone levels were possibly the lowest ever recorded, but they were
still significantly higher than the Antarctic's," Strahan said. "There
was about half as much ozone loss as in the Antarctic and the ozone
levels remained well above 220 Dobson units, which is the threshold for
calling the ozone loss a 'hole' in the Antarctic - so the Arctic ozone
loss of 2011 didn't constitute an ozone hole."
The majority of
ozone depletion in the Arctic happens inside the so-called polar vortex:
a region of fast-blowing circular winds that intensify in the fall and
isolate the air mass within the vortex, keeping it very cold.
Mineral weathering by fungi (Credit: Joe Quirk)
UK researchers have identified a biological mechanism that
could explain how the Earth’s atmospheric carbon dioxide and climate
were stabilised over the past 24 million years. When CO2
levels became too low for plants to grow properly, forests appear to
have kept the climate in check by slowing down the removal of carbon
dioxide from the atmosphere. The results are now published in Biogeosciences, an open access journal of the European Geosciences Union (EGU).
“As CO2 concentrations in the atmosphere fall, the Earth
loses its greenhouse effect, which can lead to glacial conditions,”
explains lead-author Joe Quirk from the University of Sheffield. “Over
the last 24 million years, the geologic conditions were such that
atmospheric CO2 could have fallen to very low levels – but it
did not drop below a minimum concentration of about 180 to 200 parts
per million. Why?”
Before fossil fuels, natural processes kept atmospheric carbon dioxide in check. Volcanic eruptions, for example, release CO2,
while weathering on the continents removes it from the atmosphere over
millions of years. Weathering is the breakdown of minerals within rocks
and soils, many of which include silicates. Silicate minerals weather in
contact with carbonic acid (rain and atmospheric CO2) in a
process that removes carbon dioxide from the atmosphere. Further, the
products of these reactions are transported to the oceans in rivers
where they ultimately form carbonate rocks like limestone that lock away
carbon on the seafloor for millions of years, preventing it from
forming carbon dioxide in the atmosphere.
Forests increase weathering rates because trees, and the fungi
associated with their roots, break down rocks and minerals in the soil
to get nutrients for growth. The Sheffield team found that when the CO2
concentration was low – at about 200 parts per million (ppm) – trees
and fungi were far less effective at breaking down silicate minerals,
which could have reduced the rate of CO2 removal from the atmosphere.
“We recreated past environmental conditions by growing trees at low, present-day and high levels of CO2
in controlled-environment growth chambers,” says Quirk. “We used
high-resolution digital imaging techniques to map the surfaces of
mineral grains and assess how they were broken down and weathered by the
fungi associated with the roots of the trees.” As reported in Biogeosciences, the researchers found that low atmospheric CO2
acts as a ‘carbon starvation’ brake. When the concentration of carbon
dioxide falls from 1500 ppm to 200 ppm, weathering rates drop by a
third, diminishing the capacity of forests to remove CO2 from the atmosphere.
The weathering rates by trees and fungi drop because low CO2
reduces plants’ ability to perform photosynthesis, meaning less
carbon-energy is supplied to the roots and their fungi. This, in turn,
means there is less nutrient uptake from minerals in the soil, which
slows down weathering rates over millions of years.
“The last 24 million years saw significant mountain building in the
Andes and Himalayas, which increased the amount of silicate rocks and
minerals on the land that could be weathered over time. This increased
weathering of silicate rocks in certain parts of the world is likely to
have caused global CO2 levels to fall,” Quirk explains. But the concentration of CO2
never fell below 180-200 ppm because trees and fungi broke down
minerals at low rates at those concentrations of atmospheric carbon
dioxide.
“It is important that we understand the processes that affect and
regulate climates of the past and our study makes an important step
forward in understanding how Earth’s complex plant life has regulated
and modified the climate we know on Earth today,” concludes Quirk.
This research is presented in the paper ‘Weathering by tree
root-associating fungi diminishes under simulated Cenozoic atmospheric
CO2 decline’ published in the EGU open access journal Biogeosciences on 23 January 2014.
The team is composed of J. Quirk, J. R. Leake, S. A. Banwart, L. L.
Taylor and D. J. Beerling, from the University of Sheffield, UK.
Dr. Joe Quirk
Post Doctoral Research Associate
Department of Animal and Plant Sciences
University of Sheffield, UK
Tel: +44 (0)114 22 20093
Email: j.quirk@sheffield.ac.uk
Prof. David Beerling (Principal Investigator)
Department of Animal and Plant Sciences
University of Sheffield, UK
Tel: +44 (0)114 22 24359
Email: d.j.beerling@sheffield.ac.uk
Bárbara Ferreira EGU Media and Communications Manager
Munich, Germany
Tel: +49-89-2180-6703
Email: media@egu.eu
