CHAPTER 22 | COMPARATIVE PLANETOLOGY OF VENUS AND MARS 469
Data Manipulation
Why do scientists think it is OK to visually
enhance their data? Planetary astronomers
studying Venus change the colors of radar
maps and stretch the height of mountains. If
they were making political TV commercials and
were caught digitally enhancing a politician’s
voice, they would be called dishonest, but
scientists often manipulate and enhance their
data. It’s not dishonest because the scientists
are their own audience.
Research physiologists studying knee inju-
ries, for instance, can use magnetic resonance
imaging (MRI) data to study both healthy
and damaged knees. By placing a patient in a
powerful magnetic fi eld and irradiating his or
her knee with precisely tuned radio frequency
pulses, the MRI machine can force one in a
million hydrogen atoms to emit radio fre-
quency photons. The intensity and frequency
of the emitted photons depends on how the
hydrogen atoms are bonded to other atoms, so
bone, muscle, and cartilage emit different sig-
nals. An antenna in the machine picks up the
emitted signals and stores huge masses of data
in computer memory as tables of numbers.
The tables of numbers are meaningless in
that form to the physiologists, but by manipu-
lating the data, they can produce images that
reveal the anatomy of a knee. By enhanc-
ing the data, they can distinguish between
bone and cartilage and see how tendons
are attached. They can fi lter the data to see
fi ne detail or smooth the data to eliminate
distracting textures. Because the physiologists
are their own audience, they know how they
are manipulating the data and can use it to
devise better ways to treat knee injuries.
When scientists say they are “massag-
ing the data,” they mean they are fi ltering,
enhancing, and manipulating it to bring out
the features they need to study. If they were
presenting that data to a television audience
to promote a cause or sell a product, it would
be dishonest, but scientists’ manipulation of
the data allows them to better understand how
nature works.You are accustomed to seeing data manipulated
and presented in convenient ways. (PhotoDisc/Getty
Images)22-1
■ Figure 22-4
Although it is nearly 1000 years old, this lava fl ow near Flagstaff, Arizona, is still such a rough jumble of sharp rock that it is dangerous to
venture onto its surface. Rough surfaces are very good refl ectors of radio waves and look bright in radar maps. Solidifi ed lava fl ows on Venus
show up as bright regions in the radar maps because they are rough. (Mike Seeds)Earth but not nearly as many as the moon. Th e craters are uni-
formly scattered over the surface and look sharp and fresh
(■ Figure 22-6). With no water and a thick, slow-moving lower
atmosphere, there is little erosion on Venus, and the thick atmo-
sphere protects the surface from small meteorites. Consequently,
there are no small craters. Planetary scientists conclude that the
surface of Venus is older than Earth’s surface but not as old as the
moon’s. Unlike the moon, there are no very old, cratered high-
lands. Lava fl ows seem to have covered the entire surface of Venus
within approximately the last half-billion years.