## Carbon Dioxide in the Martian Atmosphere

Spectroscopic studies of Mars, made over a period of more than 80 years, had produced no conclusive evidence concerning the nature of the atmospheric gases. All that could be said was that if certain gases were present, then their abundances must be less than various specified amounts. But there was no positive proof that these gases were present at all. Although it was quite certain that Mars had an atmosphere, and approximate estimates had been made of its pressure, nothing was definitely...

## Accel eration4 r2

Where G is the universal constant of gravitation (6.67 XI08 in the centimeter-gram-second system of units), M is the mass of the planet, and r is the radius of the planet at the point under consideration. The radii of flattened bodies, like Mars and Earth, vary with the latitude, and so, consequently, also do the gravitational accelerations. For the present purpose, however, it is sufficient to determine an average value for Mars. Thus, by using the mass (in grams) and average radius (in...

## Eccentricity

If an ellipse is imagined to become less and less elliptical, and approach a circle, the two foci must come closer together. In a circle, the foci coincide at the center of the circle then the points F1 O, and F2 in figure 3.2 are all identical. The distance OF L is zero and hence, by the definition given above, the eccentricity of a circle is zero. On the other hand, if an ellipse becomes more elliptical, and deviates more and more from a circle, the foci F and F2 get farther apart. The...

## Identification of Gases by Absorption Spectra

Sunlight passes through the Martian atmosphere, first to the planet, and then after reflection by the surface and the atmosphere. In each passage the molecules and atoms present in the atmosphere of Mars absorb radiations of characteristic wavelength, and it is by the study of these absorption spectra on Earth that information concerning the composition of the Martian atmosphere has been obtained. Of course, if a particular species does not absorb any of the radiation from sunlight or the...

## Planets and Asteroids

The planet mars is a member of the solar system that is to say, it is one of the bodies which revolve in orbits about the Sun. During the early years of the 17th century, when Kepler's views of a Sun-centered system were beginning to find acceptance, six planets were known. In order of increasing distance from the Sun, they were Mercury, Venus, Earth, Mars, Jupiter, and Saturn. These bodies are all visible, at appropriate times, by the unaided eye. In spite of the development of the telescope,...

## The Diameter of Mars

The simplest method for determining the diameter of a planet is to measure its apparent angular diameter when the planet is at a FIGURE 4.1. Determination of the diameter of FIGURE 4.1. Determination of the diameter of known distance from Earth. In figure 4.1, for example, in which the size of the planet is greatly exaggerated for clarity, the angular diameter is indicated by 0. If D is the distance from the planet to Earth and 6 is expressed in radians (1 radian 57.296 degrees of arc), then...

## The Satellites Of Mars Predictions of Martian Moons

Kepler predicted that Mars had two satellites. This prediction turned out to be correct, although its basis was highly fortuitous. One of the earliest observations made by Galileo with his telescope was that Jupiter had 4 moons, although it is now known to have 12. Furthermore, it will be recalled from chapter III that Kepler had suspected there might be a missing planet between Mars and Jupiter. Consequently, he suggested the following simple sequence for the successive...

## Martian Surface Temperatures Calculated Temperatures

An approximate idea of the maximum and average temperatures of the surface of Mars can be obtained by supposing that the planet behaves as an ideal (blackbody) emitter of radiation. The rate E at which energy is radiated from a blackbody is related to the absolute temperature T in K, which is 273 plus the temperature in C, by the theoretical (Stefan-Boltzmann) expression E 8 28 X1011 T4 cal cm7min If it is assumed that the planet has attained temperature equilibrium with its surroundings, as is...

## The Canals of Mars

The canals have been the subject of more heated and prolonged discussion than any other aspect of the planet Mars. Many reputable astronomers, following G. V. Schiapa-relli, claim to have seen the long and narrow linear markings on the surface, whereas others, equally reputable, have been unable to confirm these observations. There are some differences in the views of those who affirm that the canals exist, indicating that there is a degree of subjectivity in their identification. Thus, in...

## Difficulties In Observing Mars

Mars is a highly interesting subject for study, but it is also a difficult one. Both Earth and Mars orbit about the Sun, but Earth travels at a faster speed in a smaller orbit. Consequently, the distance between Earth and Mars is always changing. At intervals of about 26 months, however, the two planets come fairly close to each other, and these occasions, which are called apparitions by astronomers, provide the opportunity for studying Mars at moderately close range. The opportunities are not...

## Favorable and Unfavorable Oppositions

For making approximate estimates, the time between oppositions may be taken as roughly 2 years and 7 weeks. It can now be seen why the apparitions of Mars occur at intervals of a little over 2 years p. 5 . It is at these times that Mars and Earth are closest and the conditions are most favorable for observations of Mars. A contributory factor is that the planet is then directly opposite from the Sun and this provides the best conditions of visibility. Because the eccentricity of the orbit of...

## Mars Through The Telescope Early Telescopic Observations of Mars

The telescope, invented in 1608 and developed as an astronomical instrument by Galileo Galilei in Italy, in the following year, provided support for the Copernican system. If the planets did indeed move in orbits about the Sun, then Venus, which is between Earth and the Sun, should show distinct crescent, gibbous, and full phases like the Moon. Because these phases could not be seen, at least by the unaided eye, it was argued that Venus does not travel around the Sun. When Galileo turned his...