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Mars spacecraft finds an unusual glass that is exciting to scientists
By Scientific American, adapted by Newsela staff
07.21.15
Scientists have identified deposits of an unusual material known as “impact glass” on
Mars, with the help of a NASA Mars orbiter. On Earth this same material has been shown to
preserve evidence of ancient life that gets trapped inside it. This means impact glass on Mars
could provide key insights into whether Mars could ever have supported life, and if it ever did.
Kevin Cannon and John Mustard of Brown University reported the glass discovery.
When an asteroid or comet (space rocks) slams into a planet’s surface, the immense
energy of the impact can melt large volumes of rock and soil. If this liquid rock cools quickly
enough, it hardens into a solid called impact glass, instead of another substance. Unlike the glass
we encounter in daily life, this material is dark brown, almost black, and only partly transparent.
It may look like freshly cooled lava from a place like Hawaii, says Cannon, a Ph.D. student.
However, lava and impact glass are formed differently.
Because asteroids and comets routinely slam into planets throughout the solar system,
scientists have long suspected that impact glass exists on other planets. The new study supports
the idea.
Making Martian Glass On Earth
Until now, no one could be sure impact glass existed on Mars. The reason is that it gives
off only a weak spectral signal. The spectral signal is the type of light an object gives off.
Scientists identify different types of rocks on Mars by picking out the unique spectral
“fingerprints” these materials leave in sunlight reflected off the planet. Dark opaque materials
like rocks absorb lots of sunlight. Therefore, their spectral signatures in reflected light are
stronger than the signatures of partially see-through materials like impact glass, explains Briony
Horgan, a planetary scientist at Purdue University. Consequently, signals from any rocks that
might be mixed in with the impact glass could block out signals from the glass.
Cannon overcame this obstacle by making his own artificial Martian impact glass. He
mixed together powders to create a concoction with similar composition to rocks on the Red
Planet. Cannon based his recipe on data from Mars rover samples and studies of Martian
meteorites. He then melted his mixture in an oven and allowed it to harden into imitation impact
glass.
By measuring the spectral signal of this imitation impact glass, Cannon and Mustard, a
professor of Earth, Environmental and Planetary Sciences at Brown, knew precisely what to look
for on the Martian surface. Mustard scoured data collected by the Mars Reconnaissance Orbiter
in hopes of finding similar signals.
Traces Of Life Under Glass
Their search turned up a slew of previously undetected glass deposits in craters across the
Martian surface. The positions of these deposits inside the craters — on central peaks that form
when an asteroid or comet strikes the planet — demonstrates that the glass was indeed formed
during the impacts. “It wasn’t completely surprising,” Cannon said. “We thought that it should
be there, and it’s really nice to validate that.”
“I can state with a pretty high level of confidence that this new study is the first clear
detection of impact glass on Mars,” Horgan said.
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The detection of impact glass on Mars is especially exciting. Studies of similar glass on Earth
have shown it can preserve traces of life that existed both before the collision and after.
Last year, a team of geologists led by Peter Schultz of Brown reported finding plant
leaves in the impact glass of an Argentinian crater. The leaves were preserved down to the
cellular level. According to Schultz, impact glass might similarly capture and preserve bits of
organisms on Mars. This suggestion is what spurred Cannon and Mustard to conduct their
search. “There is no proof that there ever was life on Mars,” says planetary scientist Kieren
Howard of Kingsborough Community College of the City University of New York. If Mars was
once inhabited, however, the bits of life inside impact glass “might just allow for the
reconstruction of ancient environments, like time capsules.”
Earliest Types Of Life-Forms
Impact glass is not only good for giving a snapshot of life in the blasting zone at the time
of the impact; the glass itself can host tiny life-forms that move in after the dust has settled.
A group of organisms called chemolithoautotrophs (tiny primitive microbes that can
make their own food) can tunnel into the glass and live. “These guys were thought to be some of
the earliest types of life on Earth, and thought to be the types of microbes that might persist on
other planets,” says Haley Sapers of Western University in Ontario, Canada. “They’re very
primitive forms, and they basically eat rocks.”
Some of these microbes — tiny life-forms — give off an acid that allows them to
dissolve the glass and consume nourishment, or nutrients, found in the glass. As the glass
dissolves, the microbes burrow deeper, forming tiny tunnels. Although no actual
chemolithoautotrophs have ever been sighted wriggling through impact glass on Earth, Sapers
says there is strong evidence that they ate through the impact glass of a 15-million-year-old
crater in Germany.
Tunnel Evidence
So if these tiny tunnels were found in the Martian glass, could that be evidence that the
Red Planet was — or perhaps still is — home to alien life? Such tunnels would certainly create
suspicion of at least past life. According to Cannon, however, “There’s no reason to think there’s
any living life on Mars today.” Besides, Sapers says that detecting tunnels in the glass would
require returning samples to Earth. Doing this would surely kill anything still alive in the glass.
Even if Cannon and Mustard’s impact glass did not trap any bits of life, it may have
preserved atmospheric gases from the time of the collision. According to Horgan, understanding
the evolution of the Martian atmosphere over time is key to figuring out if its surface might have
supported life at one time.
INSTRUCTIONS:
CORNELL NOTE STYLE IN YOUR JOURNAL
A. Define bold-faced words
B. Answer questions:
1. What happens when an asteroid or comet hits a planet?
2. How did scientists know exactly what to look for to find the impact glass on Mars?
3. How do chemolithoautotrophs form tunnels?
4. How do the tunnels support the idea that life is present?
C. Write a summary of the article in paragraph form. In other words, what did you “get” out the article?
Name ______________________________________ HOMEWORK DUE THURSDAY!
Mars spacecraft finds an unusual glass that is exciting to scientists
By Scientific American, adapted by Newsela staff
07.21.15
Scientists have found an unusual material on Mars. It is called “impact glass.” The
discovery is important. Impact glass could help show us if anything can live on
Mars. It could also reveal if anything has ever lived on the planet.
Signs of impact glass were discovered by Kevin Cannon and John Mustard.
Cannon is a student at Brown University. Mustard is a professor at Brown. They
found the impact glass with help of a NASA Mars spacecraft.
Impact glass can be formed when a big space rock crashes into a planet. These
space rocks are called asteroids or comets. The crash creates a lot of heat. The
heat can melt rocks. When the melted rock cools it becomes solid. If it cools
quickly, the solid rock becomes impact glass. It is different than the glass we
usually think of. It is dark brown, almost black. It is only partly see-through.
Fake Glass Used To Find Real Glass
Asteroids and comets often slam into planets. Because of this, scientists have
believed that impact glass exists on other planets. The new study helps to show this
idea is true.
It has been hard to find impact glass on Mars. Scientists identify different types of
rocks on the surface of Mars by looking at the sunlight that is reflected off the
planet. Different rocks leave different marks in the reflection. The marks are sort of
like fingerprints. The fingerprint is a rock's spectral signal (The spectral signal is
the type of light an object gives off). Impact glass has a weak spectral signal.
Rocks have strong signals because they are so dark and absorb sunlight. Signals
from rocks are so strong that they can block out signals from impact glass. It can
make it hard to see the signals from impact glass.
Cannon solved this problem. He made his own fake Martian impact glass. First, he
mixed together powders that are like what rocks on Mars are made of. Then he
melted the powders in an oven. After that, Cannon and Mustard measured the
spectral signal of this fake glass. It helped them to know just what to look for on
Mars.
Their search turned up a bunch of glass in deep holes called craters on the planet's
surface. One scientist said it was the first time impact glass was found on Mars.
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Digging Into Tiny Tunnels
Impact glass has also been found on Earth.
Last year, a team of scientists from Boston University found plant leaves inside
impact glass. The glass was found in a crater in Argentina. It could mean impact
glass on Mars might also hold bits of tiny life. But there is still no proof that there
ever was life on Mars. However, if there was once life on Mars, bits of life inside
impact glass could let scientists figure out what the planet used to be like, he said.
Impact glass could also hold tiny life-forms from ancient times. The life-forms are
microbes.
Scientists think these microbes were some of the earliest life on Earth. They can
dig into the glass and live. They eat it for food.
Some of the microbes make acid. The acid melts the glass. As the glass melts, the
microbes dig in deeper. They make tiny tunnels.
If these tiny tunnels were found in the Martian glass, it could mean that there used
to be life on Mars.
Define the following:
Impact glass: ____________________________________________________
Asteroids or comets: ______________________________________________
Microbes: _______________________________________________________
Questions:
1. How is impact glass formed?
2. If tunnels are found in the Martian impact glass, what might that mean?