HELPPPPP! I PUT 45 POINTS!!!!!! QUICK!

This Tiny Animal Is Apocalypse-Proof
Asteroids or exploding stars won't wipe out microscopic critters called

tardigrades
By Maria Temming
2017

Water bears, also known as tardigrades, are eight-legged micro-organisms that can survive in apocalyptic
environments. In this informational text, Maria Temming further discusses the conditions water bears can
live through and what scientists can learn from them. As you read, take notes on the various events water
bears can survive.
Water bears might end up being the last animals
on Earth.
Also known as tardigrades, these microscopic
creatures are tough. A new study concludes that
they could survive until — several billion years
from now — the sun boils Earth’s oceans away.
That’s good news for anyone hoping Earthlings
may have company in the universe. If these
critters can live through such extreme conditions
on our planet, it suggests life might exist in other
seemingly inhospitable1
places.

Other studies had looked at threats to people from space. They focused on such things as asteroids
striking Earth, neighboring stars going supernova2

or huge explosions called gamma-ray bursts. But for
the new study, researchers ignored fragile humans. They wanted to know what it would take to wipe
out one of the world’s ultimate survivors.
So they turned to tardigrades.
The microscopic critters live all around the world. And they are hardy. Decades without food or water?
No problem. Temperatures plummeting to –272° Celsius (–460° Fahrenheit) or skyrocketing to 150 °C
(300 °F)? Bring it on. Even the crushing pressure of deep seas doesn’t bother them. Nor does the
vacuum of outer space or exposure to extreme radiation.
Water bears are so sturdy that even a nuclear war probably wouldn’t kill them. Neither would global
warming nor any astronomical events that wreak havoc on Earth’s atmosphere. But all of these
scenarios could doom humans, notes Avi Loeb. He’s an astrophysicist at Harvard University in
Cambridge, Mass.
[1]

[5]

1. Inhospitable (adjective): harsh and difficult to live in
2. the explosion of a star

1

From Science News for Students, August 9, 2017. © Society for Science & the Public. Reprinted with permission.
This article is intended only for single-classroom use by teachers. For rights to republish Science News for Students articles in assessments,
course packs or textbooks, visit: https://societyforscience.org/permission-republish

To exterminate3

tardigrades, something would have to boil the oceans away. (No more water means
no more water bears.) So Loeb and his colleagues calculated just how big an asteroid, how strong a
supernova, or how powerful a gamma-ray burst would have to be to heat Earth’s oceans that much.
“They actually ran the numbers on everyone’s favorite natural doomsday weapons,” says Seth Shostak.
He’s an astronomer at the SETI Institute in Mountain View, Calif. (One of the SETI Institute’s goals is to
search for alien life.)
Loeb’s team found that there are only 19 asteroids in the solar system massive enough to wipe out
water bears. None are on a collision course with Earth.
A supernova — the explosion of a massive star after it burns through its fuel — would have to take

place within 0.13 light-year of Earth. Yet the closest star big enough to go supernova is nearly 147 light-
years away.

Then there are gamma-ray bursts. These explosions are thought to come from especially powerful
supernovas or colliding stars. They’re also extremely rare. Over a billion years, there’s only about 1
chance in 3 billion of a gamma-ray burst killing off tardigrades, the researchers calculated.
Loeb and his colleagues published their results July 14 in Scientific Reports.
“Makes me wish I were an extremophile like a tardigrade,” says Edward Guinan. He’s an astrophysicist
at Villanova University in Pennsylvania who was not involved in the work. An extremophile is a life form
that can survive in harsh environments.
But even tardigrades can’t cheat death forever. In the next seven billion years, the sun will swell into a
red giant star.4

It might engulf Earth, and it will surely sizzle away Earth’s water.

Until then, tardigrades can probably resist any other potential apocalypse. This is exciting to
researchers who hope that if there’s life elsewhere in the universe, it lasts long enough for us to find it.
Notes Shostak, “Life is tough, once it gets going.”




1. PART A: Which statement identifies the central idea of the text?


A. There are very few unlikely events that could completely eliminate water bears.

B. Water bears’ ability to survive in space proves there are other life forms that

exist beyond Earth.

C. By studying water bears’ ability to survive extreme conditions, humans can learn

how to better protect themselves.

D. While many people believe water bears are indestructible, there are actually

several things that can kill them.