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Science and Society

Worth the Cost?
eople are fascinated with ideas of here on Earth, such as growing energy and
saved thanks to storm warnings provided
Pspace travel as well as new discoveries water needs, pollution problems, and on-
by weather satellites. There are many other
about the universe and how it formed. Un- going health problems. They say that the
spin-offs from the space program, including
manned space probes, new kinds of instru- money spent on exploring space could be
improvements in communication systems.
ments, and new kinds of telescopes have better used for helping resolve problems
resulted in new information. We are learn- on Earth.
ing about what is happening in outer space In addition to new information and QUESTIONS TO DISCUSS
away from Earth, as well as the existence of understanding, supporters of the space pro-
other planets. gram point to new technology that helps 1. Have the gain of knowledge and the
Few would deny that the space pro- people living on Earth. Satellites now pro- spin-offs merited the expense?
gram has provided valuable information. vide valuable information for agriculture, 2. Alternatively, would the funds
Some people wonder, however, if it is worth including land use and weather monitor- be better spent on solving other
the cost. They point to many problems ing. Untold numbers of lives have been problems?

provided data about the early environments and conditions that
have existed on Mars. After the Pathfinder lander completed its
primary 30 day mission and fell silent, it was renamed the Carl
Sagan Memorial Station.
The Mars Exploration Rovers, named Spirit and Oppor-
tunity, landed on Mars on January 4 and January 25, 2004, to
answer questions about the history of water on Mars. The space-
craft were sent to sites on opposite sides of Mars that appear to
have been affected by liquid water in the past. After parachute
and airbag landings, the 185 kg (408 lb) rovers charged their
solar-powered batteries. They then began driving to different
locations to perform on-site scientific investigations over the
course of their mission (Figure 15.6).
What did the rovers find? They found that Mars was made
of basalt rock (see chapter 17) and groundwater that was dilute
sulfuric acid. The acid interacted with the rock, dissolving things
out of it, and then evaporated, leaving sulfur-rich salts. The Spirit
and Opportunity rover results confirmed that sufficient amounts of
water to alter the rocks have been present in the past ( Figure 15.7).
The results also confirm interpretations of remote sensing data
made before the actual mission. This provides evidence that
other present and future remote sensing data are accurate.
The presence of past or present life on Mars remains an
open question. Scientists already knew there was liquid water in
the past, and water and life go together. Beyond that, the Rover
mission has really not changed the prospect of finding evidence
of past or present life, so the search goes on.
Mars was named for a mythical god of war, so the two satel-
lites that circle Mars were named Deimos and Phobos after the FIGURE 15.6 Researchers used the rover Spirit’s rock abrasion
two companions of the Roman god. Both satellites are small, tool to help them study a rock dubbed “Uchben” in the “Colombia
irregularly shaped, and highly cratered. Phobos is the larger of Hills” of Mars. The tool ground into the rock, creating a shallow
the two, about 22 km (about 14 mi) across the longest dimension, hole 4.5 cm (1.8 in) in diameter in the central upper portion of this
image. It also used wire bristles to brush a portion of the surface
and Deimos is about 13 km (about 8 mi) across. Both satellites
below and to the right of the hole. Spirit used its panoramic camera
reflect light poorly and have a much lower density than Mars. during the rover’s 293rd Martian day (October 29, 2004) to take
They are assumed to be captured asteroids rather than naturally the frames combined into this approximately true-color image.
occurring moons. Source: NASA/1PL/Cornell.

384 CHAPTER 15 The Solar System 15-8