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NATIONAL ACADEMY OF SCIENCES NATIONAL ACADEMY OF ENGINEERING INSTITUTE OF MEDICINE NATIONAL RESEARCH COUNCIL
June 18, 2004 Current Operating Status
International Cooperation for Mars Exploration and Sample
Return
1
Introduction
The goals of planetary exploration are to understand the origin and evolution of the
solar system, how the planets formed, and how the planets evolved to their present
states and environments. The history and evolution of Earth indicate that life can
have profound effects on the development of a planet's surface and atmospheric
environment. Parallel goals are to understand the chemical precursors of life and
the conditions that led to the origin of life on Earth and to ascertain the prevalence
of analogous prebiotic or biotic environments elsewhere. Altogether, planetary
exploration seeks to answer questions that are fundamental to our understanding
of our existence on Earth, as well as to the present state of our planetary
environment and its evolution.
These planetary questions have stimulated human thought and scientific
investigation throughout history. They continue to be among the most basic and
pressing of scientific questions today. Thus planetary exploration has been
recognized as a fundamental element of the U.S. space program and as a source
of great international prestige. Investigation of the terrestrial planets has been put
forward by the Space Studies Board (SSB) as a principal focus of planetary
exploration1; the importance of terrestrial planet studies has subsequently been
reiterated in program implementation plans put forward by the National Aeronautics
and Space Administration (NASA) 4,5 and by the SSB. 6 In the context of this
focus, it is recognized that Mars occupies a special position as a target for
intensive investigation.
The triad of terrestrial planets—Earth, Mars, and Venus—has been a major target
of investigation by both the United States and the USSR because these three
terrestrial planets pose a particularly sharp set of scientific questions and because
their proximity makes them attractive targets for investigation. Earth, Mars, and
Venus are similar in their sizes, masses, compositions, and locations with respect
to the Sun. Yet these planets have evolved to have widely (different surface
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conditions in ways that are of special interest to human beings, whose existence
and survival depend on the special surface conditions of Earth. Studies of these
three planets have already revealed that terrestrial planet environments may
change their states in highly unstable ways. It is possible that, at times past, the
conditions on both Mars and Venus may have been more similar to present-day
terrestrial conditions. It is important to understand the possible varieties and
causes of changes in terrestrial planet environments, especially today, when
human perturbations of Earth's environment are no longer negligible and are
growing larger.
In these three planets we observe three natural experiments in planetary evolution.
One experiment produced the Earth, where abundant free water on its surface and
in its atmosphere has enabled the origin and persistence of life. Another
experiment produced Venus, where most of the outgassed volatiles remained in a
carbon-dioxide-rich atmosphere but where the water apparently escaped. And the
third experiment produced Mars, which either has lost part of its atmosphere or
never had one of large substance, but which has undergone extraordinary
environmental change.
For these reasons, investigation of the triad of terrestrial planets with persistent
atmospheres has very high scientific priority, The primary scientific objective of
studying this group of terrestrial planets is to understand the reasons for their
diverse evolutions and their very different present environments. An additional
motivation for giving a high priority to the investigation of terrestrial planets is that
such investigations will illuminate our understanding of the planet Earth.
Early investigations of Mars, undertaken in the U.S. space program during the past
20 years, have revealled that that planet poses numerous profound questions
about the behavior of terrestrial planets and their environments. Evidence of broad
climatological changes, apparently encompassing ancient temperate episodes with
flowing water as well as the cold dry conditions that we observe today, challenges
our understanding of the behavior of planetary environments and raises questions
about the stability of planetary environments, including that of Earth. Moreover,
from a practical point of view, after Earth, Mars is the terrestrial planet most
accessible to investigation, because of both its proximity and its relatively benign
surface conditions. Altogether, the intensive investigation of Mars offers a broad
spectrum of important scientific reward, technical challenge, and opportunity.
The National Research Council's Space Studies Board has recommended that the
next major phase of Mars exploration involve detailed in situ investigations of the
surface of Mars and the return to Earth for laboratory analysis of selected martian
surface and subsurface samples. 1 Mars sample return and intensive Mars surface
investigation have been accepted by NASA as essential to accomplishing very-
high-priority terrestrial planet scientific objectives within a balanced program of
planetary and space science and have been included in NASA planning by NASA
and its internal advisory panels. 4,5 In addition, Mars exploration is of wide
scientific and technical interest in several other nations. 7 A Mars surface rover
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project, recognized as a necessary element of a Mars sample return program, has
been identified as a desirable candidate for joint NASA-European Space Agency
(ESA) collaboration by the U.S. National Academy of Sciences-European Science
Foundation Joint Working Group on Cooperation in Planetary Exploration.a The
ESA has also expressed general interest in a broader program of cooperative Mars
exploration and sample return. The USSR has announced national plans for an
extensive program of Mars investigation that incorporates substantial international
cooperation.
The present Committee on Cooperative Mars Exploration and Sample Return was
established at the request of NASA. The charge to the committee was to examine
and report on the question of how Mars sample return missions might best be
structured for effective implementation by NASA along with international partners.
The committee considered alternatives ranging from scientific missions in which
the United States would take a substantial lead, with international cooperation
playing only an ancillary role, to missions in which international cooperation would
be a basic part of the approach, with the international partners taking on
comparably large mission responsibilities. The committee considered the scientific
basis of such collaboration and the most mutually beneficial arrangements for
constructing missions of separate supporting elements. Although the committee
considered the possibility that the United States would play only a minor role while
intensive Mars exploration was carried on by other nations, this alternative is not
treated in detail in this report. The committee agreed with previous
recommendations of the Space Studies Board as to the importance and priority of
intensive Mars exploration and sample return and took as a premise the desirability
of a high level of U.S. participation.
The Joint Working Group on International Cooperation in Planetary Exploration
also reported specific details of recommended candidate joint projects and made
specific recommendations as to the types of cooperation that could serve as a
basis of U.S.-European joint projects in several aspects of planetary exploration,
including the investigation of Mars.8 The recommendations for U.S.-European
cooperation in planetary exploration were based on the relatively long record of
experience with various levels of cooperation between U.S. and European
scientists and between NASA and the several European space agencies. Those
recommendations also took into account the long tradition of open communication,
travel, cooperation, and technical exchange that has existed between Western
Europe and the United States.
For reasons given in Chapter 2, the United States and the USSR occupy unique
positions with respect to the intensive levels of exploration associated with the next
steps of Mars exploration and Mars sample return. Because of this, the present
study has focused on developing policy recommendations for possible cooperation
between the United States and the USSR, specifically in the context of strongly
stated interests by both nations in conducting intensive scientific explorations of
Mars that include in situ investigations at Mars and the return of samples to Earth
for laboratory analysis. The high scientific importance that is attached to such
intensive studies of the planet Mars, the ambitious nature of the needed Mars
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investigations, and the fact that the two leading spacefaring nations have both
expressed strong interest in and have announced plans for Mars investigations
create a strong motivation to explore possible means of cooperation in this historic
and consequential endeavor.
The scope of the present study and the recommendations in this report have
purposefully been constrained to deal with those issues that are especially
pertinent to the specific question of U.S.-USSR cooperation in a program of Mars
investigations with sample return. A great many other issues and questions arise
that are not dealt with in detail in this report. Many of these issues—including the
pertinent scientific objectives and the detailed strategy of investigating Mars and
collecting surface samples—have been addressed in previous scientific policy
reports of the National Research Council 1,8 and in implementation plans of NASA
and are not taken up further here. This report relies on those earlier
recommendations to define the scientific context within which U.S.-USSR
cooperation would take place.
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