from a manned lander would meet the roving vehicle, offload the samples to the LM, and then use the roving vehicle to do the detailed geologic investigations of the edge of the Basin, the Mountain Front, and the nearby Rille.

In order for this Nation to accomplish an effective program of lunar exploration, four basic elements are desirable: mobility, staytime, emplaced geophysical stations, and orbital surveillance. Some of these elements can be provided by modifying Apollo systems. Some of these modifications are well along in terms of definition. A few are still concepts. Supporting automated systems are also being studied intensively.

In 1970 we will be conducting the basic scientific research and related technology which is essential to hold open the options to do the kind of lunar exploration I have just described. This effort must address itself to a spectrum of problems from the more immediate practical question (e.g., understanding the effect of radioactive elements on the internal temperature of the Moon). Some of the resources will be used to support the development of new or modified geochemical or geophysical instruments as potential candidates for future missions, either on the Moon or to the planets.

In summary, we are moving rapidly forward in developing the capabilities of man to explore the Moon. We expect to land man on the Moon in 1969 and to return samples to the Earth for analysis. We expect to use man to place scientific instruments on the Moon and to make observations and descriptions of what he sees. We have developed scientific instruments for the first few landings on the Moon and they are now ready. Funds are required at this time, however, to define the next generation of scientific instruments, to analyze and interpret the Apollo data, to get ready for the next phase of lunar exploration, and to maintain our scientific competence.

PLANETARY PROGRAM

The basic scientific goals of the Planetary Program are to increase our understanding of: (1) the origin and evolution of the solar system, (2) the origin and evolution of life in our solar system, and (3) the dynamic processes that

shape man's terrestrial environment. The third goal may be restated as-increasing our understanding of the planet Earth as it exists today, how it has evolved, and how it may evolve in the future through a comparative study of the other planets in the solar system.

We inhabit one of nine planets circling the sun (Chart SI69-518). These planets range in size from 3,000 miles in diameter (Mercury) to 89,000 miles in diameter (Jupiter) for reference, the Earth's diameter is about 7,800 miles). Mercury, Venus, Earth and Mars, the four planets closest to the Sun, are called "terrestrial" or Earthlike, because of their similarity in size and density. The next four planets-Jupiter, Saturn, Uranus, and Neptune-are classified as Jovian, or Jupiterlike. While they are much larger than the terrestrial planets, their densities are considerably less. Little is known about Pluto, but is thought to be terrestrial in size and density.

Since the time of Galileo, man has studied the Moon and the planets in the solar system with telescopes. For centuries, man has also explored his own planet, the Earth. Nevertheless, we do not know how the planets originated, how they evolved, and how, for example, the continents and oceans on Earth were formed.

We do know that the planets are similar in some respects and yet, are different in most respects. The features of the four planets nearest the Earth or "near" planets are summarized in Chart SL69-398. Mars is a dynamic and colorful planet. The light surface areas are reddish-orange in color, which presumably led early astronomers to name the planet after the Roman god of war. The darker areas, which cover about one-third of the planet's surface, are observed as varying shades of green, blue, brown, and gray; these areas exhibit the socalled "wave of darkening" which occurs as the polar caps recede during the Martian spring and early summer. The biologists believe that Mars represents the best prospect for harboring extraterrestrial life in the solar system.

Beyond Mars is the immense planet Jupiter. Even the moons of Jupiter are extraordinary. Two of its satellites are as large as the planet Mercury and may have atmospheres of their own. Jupiter is so large that in many ways it is more lake a star than a planet. For example, it appears that Jupiter generates energy internally and radiates more energy than it receives from the Sun. The great Red Spot on Jupiter larger in dimensions than the Earth, has been observed for centuries; yet very little is known about it.

Venus has a size, density, and gravitational force very similar to those of the Earth, and yet it has an exceedingly dense atmosphere of carbon dioxide and is very hot at the surface. The real puzzle about Venus is how so many of its properties can be so similar to the Earth's and yet others be so very different.

Closest to the Sun is tiny Mercury. Relatively little is known about Mercury because it is very difficult to observe with a telescope. It has an unusually high density for a terrestrial planet and rotates very slowly about its axis.

It is the understanding of these differences among the planets which promises to increase our understanding of the origin and evolution of the solar system and of life itself. While striving toward these goals, we should be able to relate our findings about the other planets to our knowledge of Earth. For example, on Mars and Venus we have found that the transfer of energy by radiation plays a major role in the atmospheric dynamics, and this may lead to a better understanding of the role of radiation on the Earth's weather. Other findings that may have application to studies of the Earth include the large diurnal atmospheric motion on Mars, the circulation of the Vensus atmosphere, and the "greenhouse" effect on both Mars and Venus. If we are to understand our own atmosphere and to evaluate the long-term consequences of manmade changes (such as the increase in carbon dioxide content), we need to conduct comparative studies of the atmospheres of the other planets.

Past Accomplishments

As we have gained new knowledge concerning the Earth during the first 10 years of the space age, we have also begun the important comparison of the other planets in the solar system to the Earth. With small, sophisticated spacecraft (Chart SL69-299), we have obtained closeup glimpses of Venus and Mars to contribute to our perspective. In addition, we have explored the interplanetary medium and better understand the influences of phenomena, such as the solar wind, on the Earth, Mars, and Venus.

During the past 10 years, major advances have also been made in laboratory research and in ground-based observations (Chart SL69-301). Optical telescopes have been used to produce a wealth of photographs monitoring the temporal variations on the planets such as the seasonal changes on Mars. When

outfitted with spectrometers and interferometers, the optical telescopes have obtained data on the atmospheric constituents of the "near" planets. Radar observations have yielded an accurate measure of the diameter of Venus, and have provided the first indications of its surface roughness.

Strategy for Planetary Exploration

In 1968, NASA, with the assistance of the Lunar and Planetary Missions Board (LPMB), carefully considered alternate approaches to the future exploration of the planets. These considerations were based upon the goals and objectives, current knowledge of the planets, anticipated new knowledge of the planets, and the probable surprises, past experience, and projected technological capabilities.

First, there was the question of which planets to explore, in which order, and with what relative emphasis. One strategy would call for the exploration of only one planet at a time. Another would be to perform simultaneous, but cursory, examination of as many planets as possible. It was concluded that neither of these strategies is appropriate; rather, the preferred strategy is one which provides for the broad-based exploration of several planets in an orderly manner over a period of time combined with direct measurements on the surface of Mars. A key element of such a "balanced" strategy is that the exploration of Mars would not preclude the more far-reaching elements of the broad-based exploration. The next question on overall strategy has to do with the methods for planetary exploration. We believe that the balanced approach also applies to the size and complexity of the spacecraft to be employed, to the types of missions to be performed, and to the role of Earth-based observations. A balanced program should include flyby missions to the more distant planets, and orbiter, atmospheric probe, and lander missions to the near planets. In addition, a mix of small, relatively inexpensive spacecraft with large, relatively more expensive spacecraft is highly desirable, as the exploration of the Earth from space has demonstrated. Likewise, much can be done by means of Earth-based astronomical observations and this technique should be fully exploited.

The Planetary Program contained in the fiscal year 1970 budget request (Chart SL69-287) represents the early phases of the balanced strategy.