Cosmic Connection: An Extraterrestrial Perspective [1973, 1975] by Carl Sagan

Author:Carl Sagan [Sagan, Carl]
Language: eng
Format: epub
Tags: DCC 523.13, LCC QB54 .S24
Publisher: Dell Publishing [mass market pbk, present ePub source]
Published: 1972-12-31T16:00:00+00:00

19. The Lost Pictures of Mars

The Mariner 9 mission to Mars radioed back to Earth 7,232 photographs that revolutionized our knowledge about the planet. Many hundreds of these pictures were devoted to studying variable features, the time changes in the relative configurations of bright and dark markings on the surface of the planet now known to be due largely to wind-blown dust. We have found thousands of bright and dark streaks, beginning in local impact craters and stretching across tens of miles of Martian surface. They point in the direction of the prevailing winds. We think they are produced by high winds carrying dust out of the craters and depositing it on the surface beyond the crater ramparts. These streaks are natural wind-direction indicators and, perhaps, anemometers laid down on the Martian surface for our edification and delight. We have discovered dark irregular patches or splotches, mostly residing in the interiors of craters, which tend to lie on the leeward walls of the craters. Thus, the splotches as well as the streaks are wind indicators. Some of the splotches have been resolved by Mariner 9 into enormous fields of parallel sand dunes.

We have discovered many cases of dark streaks and splotches varying through the mission in outline or extent. The positions and variabilities of these dark features correspond well to the classical dark markings of Mars, observed by ground-based astronomers for more than a century and most often attributed by them to seasonally changing dark vegetation on the Martian surface. But our Mariner 9 evidence points unambiguously to a meteorological, rather than a biological, explanation of the Martian seasonal changes.

This in no way excludes life on Mars. It merely means that if there is life on Mars, it is not easily detectable over interplanetary distances. The same is true in reverse: Photographic detection of life on Earth in daylight from the vantage point of Mars is impossible, as we have found by studying several thousand orbital photographs of our own planet. But the time-varying streaks and splotches on the Martian surface are a new and most exciting Martian phenomenon, which cries out for further study.

Since the Martian changes occur slowly, the variable-features objectives required very long time intervals between two pictures of the same region to see what changes had occurred. At the very end of the mission, fifteen photographs were successfully taken by the Mariner 9 cameras of regions in Syrtis Major and Tharsis, important for understanding the long-term variations. But when the time came to point the high-gain antenna of Mariner 9 to the Earth, so that these pictures could be transmitted by playing back the spacecraft’s tape recorder, the last of the attitude-control gas was used up, Earth-lock could not be acquired, and playback did not occur. The spacecraft had literally run out of gas.

About a year before the Mariner 9 mission was launched, the possibility was raised that the spacecraft would run out of control gas. A solution was proposed: That the propulsion tanks be connected to the attitude-control gas system–a kind of spacecraft anastamosis.

Download

Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.