Friday, July 20, 2012
First Martian was a Viking
Following this theme of space travel, we now jump ahead seven years to 1976, where we find the Viking I probe has just landed on the surface of Mars after a ten month cruise. It took about three hours for the Lander to touch down after separating from the Orbiter portion and flying through Mars' thin atmosphere. This photo is the first of its transmissions back to Earth (sent 25 seconds after landing and taking approximately 4 minutes to reach us), which continued for another 6 years, 116 days before being terminated. The overall mission for Viking I began with its launch on August 20, 1975 and ended on November 13, 1982.
The original plan was to have the Viking I land on July 4, 1976, America’s 200th birthday (great present, right?), but imaging of the primary landing site showed it to be too rocky, and it took another sixteen days to find a safer location. This was the United States first attempt at landing on Mars.
The amazing shot above is a martian sunset over Chryse Planitia (Golden Plain in Greek). Chryse Planitia is a circular plain in the northern equatorial region of Mars, thought to be an ancient impact basin. There is evidence of water erosion in the past, as this is the bottom end for many outflow channels. This basin is one of the lowest regions on Mars (2-3 km or 6,562-9,843 ft below mean surface elevation). In fact, the Viking program (consisting of this and one other probe) provided strong evidence for a great deal of running water on the surface of the planet after discovering several ancient river valleys.
Mars is the fourth planet from the sun, an average of 225 million km from Earth. I say average because the orbital path of Mars around the Sun is elliptical rather than circular; this means that the Sun isn’t at the center of the orbital path, it’s at one end. An easy way to understand this is to draw an egg shape on a piece of paper. This represents the path Mars travels around the Sun. Now put a dot at one end of the egg; that’s the Sun. So there are times when Mars is close to the Sun, and times when it’s far away, just like Earth. In theory, Mars is closest to Earth when it’s closest to the Sun, and Earth is at its farthest point from the Sun.
Ok, that’s enough of the complex scientific stuff. Here are some more Mars facts that you may find interesting. A year is how we measure the number of days it takes to orbit the Sun once right? Well for Mars it takes 687 Earth days, not quite twice as long. To put this in perspective, here’s a bit of math for you: including today, I am 11,534 days old (about 31.6 years). If I were living on Mars, I would only be about 16.8 years old. (To find your own approx. Mars age, multiply your age in years, plus months since your last birthday, by 365, then divide by 687. Or, send me a message with your date of birth and I’ll figure it out for you.)
Also, Mars is about half the diameter of Earth, with a surface area slightly less than the total of Earth’s dry land. It has a terrestrial surface like ours, with a thin atmosphere, and surface features similar to the Moon and Earth’s polar ice caps. Jupiter, Venus, the Moon, and the Sun are the only “heavenly bodies” brighter than Mars, which can be seen with the naked eye. Finally, Mars has two small moons, named Phobos and Deimos, which are irregularly shaped.