快猫短视频

IT鈥橲 blamed for obliterating the dinosaurs, but that famous asteroid or comet
impact did more鈥攊t sprinkled buckyballs containing extraterrestrial gases
all over the Earth. 快猫短视频s say this backs the idea that earlier impacts
enriched the primeval soup of organic chemicals that gave rise to life.

Several years ago, Luann Becker and Jeffrey Bada of the Scripps Institution
of Oceanography in San Diego found buckyballs鈥攖iny cages of carbon
atoms鈥攊n the debris of an impact crater in Canada. Trapped inside these 60
and 70-carbon molecules was a mixture of helium isotopes more typical of
interstellar space than Earth鈥檚 atmosphere, hinting that they formed in space
and travelled to Earth on the meteorite
(快猫短视频, 20 April 1996, p 17).

But critics argued that all these buckyballs might have formed in the heat of
the impact, or in wildfires that followed it. So to find out more, Becker and
her colleagues have looked at debris from another impact: the one thought to
have wiped out the dinosaurs 65 million years ago. Debris from this bombshell,
which sprayed into the atmosphere and rained down all over the world, is
preserved in ancient sediments.

In samples of this debris from New Zealand, Denmark and Colorado, and in
samples from two meteorites, Becker鈥檚 team has again found buckyballs鈥攕ome
as large as C₄₀₀. When opened up in the lab, these contained mixtures
of inert gases that the team says 鈥渃an only be described as extraterrestrial in
origin鈥�. 鈥淲e鈥檝e pretty much nailed it this time,鈥� says Becker, now at the
University of Hawaii in Honolulu.

She adds that if organic compounds could survive the plunge to Earth, this
supports the idea that early impacts enriched the primordial soup of chemicals
that gave rise to life. And buckyballs that have survived might provide the best
record of Earth鈥檚 impact history, giving clues to unexplained mass extinctions
such as the one 250 million years ago. 鈥淚t was close to complete sterilisation,
wiping out nearly every living organism on the planet,鈥� says Becker. 鈥淏ut so far
there鈥檚 no evidence for an impact.鈥�

The work should also help astronomers to pinpoint the birthplaces of
buckyballs in space. 鈥淢eteorites are like the garbage cans of the
Universe鈥攖hey pick up everything that鈥檚 out there and give you hints about
how they formed,鈥� says Becker. Buckyballs could have formed in the atmospheres
of old stars called red giants in the twilight of their lives.