12.Practice.Tests.for.the.SAT_2015-2016_1128p

Section 31
Practice Test Five
421
Questions 16-24 are based on the following passage.
The fo llowing passage is adapted from a NASA resea : cher's
position paper on the possibility of human colonization
of Mars.
While Venus is commonly called Earth's sister
planet, its proximity to the Sun causes surface
temperatures of 900 degrees Fahrenheit, too hot
Line to support life. Alternately, due to distance from
(5) the Sun, every planet past Mars is too cold. Thus,
Mars is the only planet in our solar system, other
than Earth, that might be able to support life.
While many scientists believe that life may have
existed on Mars in the past, some are now begin-
(10) ning to believe that human life may be able to
exist there in the future, but not without earthly
intervention.
Scientists have long envisioned human colonization
of Mars in space station-like enclosed
(15) structures, but some are now beginning to believe
in the possibility of altering the Martian climate
and atmosphere to create an Earth-like world
where humans can live unencumbered by pressurized
suits or structures. These scientists point out
(20) that before it supported life, Earth was, like Mars,
a desolate, uninhabitable planet devoid of oxygen.
This situation only changed with the evolution of
photosynthetic bacteria that absorb carbon dioxide
from the atmosphere and release oxygen back
(25) into it. These scientists postulate that a similar
catalyst could be used to transform the Martian
atmosphere into one inhabitable by humans.
Such a process, called terraforming, would take
decades, if not centuries or even millennia, and
(30) involve technology not yet developed.
Warming stands as the first domino in terraforming
Mars. Since Mars is about 50 percent
farther from the Sun than is Earth and has only 1
percent as much atmospheric pressure, Martian
(35) surface temperatures average minus 81 degrees
Fahrenheit. Since it is theoretically impossible to
move Mars into a warmer orbit, scientists have
concluded, ironically, that the same process many
blame for harming life on Earth, global warming
(40) caused by greenhouse gasses, must be used to
terraform Mars. Scientists have postulated three
methods for releasing greenhouse gasses into
the Martian atmosphere to begin the process of
Martian warming.
( 45) Large orbital mirrors can be used to reflect sunlight
onto the Martian surface. NASA scientists
have invested large amounts of research into the
development of such mirrors for use as solar sails,
which capture the Sun's radiation in order to
(50) propel a spacecraft. NASA could easily decouple
solar sail technology from propulsion systems in
order to use the large mirrors for terraforming
Mars. Unfortunately, each mirror would need to
be at least the size of West Virginia in order to
(55) reflect enough sunlight to warm even a small area
of the Martian surface. Additionally, such mirrors
would weigh over 200,000 tons, meaning they
cannot be launched from Earth. However, such
mirrors could be constructed in and from materi-
(60) als found in space. Furthermore, once constructed,
the mirrors can be concentrated at the Martian
polar ice caps in order to melt the ice and release
the large reservoirs of native carbon dioxide that
scientists believe to be trapped there.
( 65) Crashing large asteroids, mostly comprised of
frozen ammonia gas, onto the Martian surface
would release large amounts of that gas, a powerful
greenhouse agent, into the atmosphere. The
engineering required for this process lies within
(70) reach. The massive thermonuclear rockets needed
to push the asteroids closer to Mars before gravity
pulls them into collision can and probably
will be developed at some point during the 21st
century. Nevertheless, astrophysical complica-
(75) tions overshadow the engineering. It would be far
too difficult to move one of these rocks from the
asteroid belt near Mars. Since objects closer to
the Sun orbit faster than objects farther from the
Sun, asteroids from farther orbits, near Pluto's,
(80) would have to be used. Not only would reaching
these more distant objects take a long time, but it
has not, as of yet, been proven that these objects
exist in the outer solar system, even though most
scientists think they do. Furthermore, while
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