The Case for Mars: The Plan to Settle the Red Planet and Why We Must by Robert Zubrin

Author:Robert Zubrin [Zubrin, Robert]
Language: eng
Format: epub
ISBN: 9780684835501
Google: 4dxmzgEACAAJ
Amazon: 0684835509
Goodreads: 56713
Publisher: Free Press
Published: 2011-01-24T23:00:00+00:00

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FOCUS SECTION—A CALENDAR FOR THE PLANET MARS

Martian colonists will need a calendar that is tied to physical and seasonal conditions on the Red Planet—using Earth dates just won’t do. If I tell you it is February 1, you know that it is freezing in Minneapolis and high summer in Sydney, but what does it tell you about conditions on Mars? In fact, the need for a Martian calendar and timekeeping system is already upon us because of current and planned unmanned exploration missions. You know the season on Earth now and can predict it with ease for any date named in the future, but without a Martian calendar you’ll be hard pressed to do the same there. So we might as well remedy this right now.

Here is the problem: Mars has a year consisting of 669 Martian days, or “sols.” As we have seen, the correct method to measure time within these days is to use units 1.0275 times longer than their terrestrial counterparts. But equipartitioned months don’t work for Mars, because the planet’s orbit is elliptical, which causes its seasons to be of unequal length.

In order to predict the seasons, a calendar must divide the planet’s orbit not into equal division of days, but into equal angles of travel around the Sun. If we want months to be useful units and choose to retain the terrestrial definition of a month as a twelfth of a year, then a month really is 30 degrees of travel about the Sun. But what to name them? Using the current terrestrial month names could be confusing, and a totally new system would be completely arbitrary. There is, however, a set of names available that has long been universally known to humanity and that has real physical significance not only for Mars, but for any planet in our solar system—the signs of the zodiac. All the constellations of the zodiac lie in the plane of motion of all the planets. Ancient astrologers, having a geocentric point of view, named the months for whatever zodiacal constellation the Sun appeared to be located in as viewed from Earth. An interplanetary culture, though, must adopt a heliocentric—or Sun centered—point of view. Therefore, I have chosen to name the Martian months for whatever constellation Mars would be found in as seen from the Sun. For Martian colonists then, the sign of the month would be seen high in the sky during the midnight hours of a given month. It is currently the custom among planetary scientists to start a planet’s year with the vernal equinox (the beginning of spring, March 21, in the Earth’s northern hemisphere), and so, consistent with that custom, the Martian year begins with the month of Gemini and ends with Taurus. The complete Martian year is given in Table 6.3.

TABLE 6.3

The Mrtian Year

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