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Course: NASA > Unit 3
Lesson 2: Mars: Ancient observationsEarly speculations
A planet for all seasons
William Herschel (1738-1822) had many opportunities to observe Mars in 1783 with the aid of his unrivaled reflecting telescopes. Below is a picture of Herschel's grand telescope:
This is an approximate view of what Mars could have looked like during ideal conditions. Notice anything interesting?
Herschel noticed both of Mars’ polar caps, as well as the slight tilt in the axis of Mars’ rotation. With the optical power of his telescopes, Herschel was able to give the most detailed evidence that Mars, like Earth, experiences seasonal changes. Herschel noted and measured that Mars has an axial tilt of 30 degrees. Today we know that the actual value of this axial tilt is 25.19 degrees.
Herschel showed that the tilt of Mars’ axis was very similar to Earth’s (23.4 degrees), and that Mars’ seasons must occur for the same reasons. However, due to the known orbital period (687 days), Herschel suggested that these seasons should occur at twice the length of those on Earth. Remember, it's the tilt of the Earth which causes us to experience distinct seasons.
Need more information on seasons? Check out Sal's playlist here
In 1784, Herschel reported to the Royal Society:
"The analogy between Mars and the earth is, perhaps, by far the greatest in the whole solar system. The diurnal motion is nearly the same; the obliquity of their respective ecliptics, on which the seasons depend, not very different … the bright polar spots are owing to the vivid reflection of light from frozen regions; and that the reduction of those spots is to be ascribed to their being exposed to the sun."
Mars began to look more and more like our twin planet…
Mars mania
A good time to get a close-up look of Mars is during opposition. This celestial event occurs about every 26 months when Mars and the Sun are on directly opposite sides of Earth (you could draw a straight line from the Sun to Earth to Mars when they are in this orbital configuration). However, the very best opposition occurs when Mars is also at its closest point to the Sun (perihelic opposition). This special alignment happens every 15 - 17 years. Even then, there are variations in distances.
Ancient observers eagerly anticipated perihelic oppositions, because they were ideal times to test out the best telescopes available. On September 5, 1877, Mars came to a perihelic opposition in the constellation Aquarius, approaching to within 35 million miles (56 million km) of the Earth. During this event Italian astronomer Giovanni Virginio Schiaparelli used a powerful telescope to produce the first detailed map of Mars.
In this picture, we can see that he identified and named several features known today. Hellas (Hellas = Greece), for example, is the largest visible impact crater in the solar system. As he tried to resolve and describe more and more detail, Schiaparelli hypothesized about the features he observed. Schiaparelli used the Italian word for channels ("canali") to describe streaks he recorded on the Martian surface. Others mistranslated this description into English as "canals," which implies structures constructed by intelligent life, in this case supposed “Martians.” His observations lead to a Mars mania which swept through Europe and America.
Driven by these new mappings of Mars and his own enthusiasm for the idea of intelligent life on Mars, Percival Lowell built the Lowell Observatory at Flagstaff, Arizona, making his first observations of Mars in 1894. His notebooks show that he observed bright and dark areas, a hint of polar caps, and canals. He assumed that an intelligent society of Martians constructed them. Below is an actual photo of Mars taken in 1907 from Lowell’s Observatory:
Lowell imagined this world as an arid desert, similar to the Earth’s desert. As he put it:
“Mars has an atmosphere; we have reason to believe this atmosphere to be very thin,--thinner at least by half than the air upon the summit of the Himalayas,--and in constitution not to differ greatly from our own.”
And of water he wrote:
“After air, water. If Mars be capable of supporting life, there must be water upon his surface; for, to all forms of life, water is as vital a matter as air. On the question of habitability, therefore, it becomes all-important to know whether there be water on Mars.”
Early telescopic observations of Mars showed dark surface features that changed over time. Some interpreted these changing patterns as vegetation growing and dying with the seasons on Mars.
This animation shows actual images of the surface of Mars during the period from August 3, 2003 to September 5, 2003.
Myths abound, what was needed was scientific evidence. Observations which can be repeated and confirmed by others. First we simply wanted to see our twin in detail, then take its temperature, reach out and touch it, smell it and determine what it’s made of and who or what, if anything lived there. To do this extensive study, we needed to extend our reach in ways that would have been unimaginable before the space age.
Want to join the conversation?
What is mars's atmosphere made up of?(11 votes)
Mars's atmosphere is made of carbon dioxide with an atmosphere that is 100 times thinner than Earth's making it colder.(3 votes)
Where could we spot Mars in the night sky because I would like to enjoy the view.(6 votes)
You can use an online planetarium to find what planets are visible throughout the night and where they are. Here is one such site: https://in-the-sky.org/skymap.php
Set it for your location if it isn't set correctly. If you turn on the selection for Ecliptic, it will show a yellow line where the planets, moon and sun are usually found near.(6 votes)
how is the polar ice caps able to melt if it is not that close to the sun?(5 votes)
The polar icecaps are predominantly (mostly) solid carbon dioxide and water ice, they sublime (turn directly into gasses rather than liquid) into gasses when warmed rather than melt. Mars has a very low atmospheric pressure so water cannot exist as a liquid on the surface, it would be a gas or a solid.(3 votes)
In the last few paragraphs when you talk about the surface of Mars and how the little dark spots move, can you explain why they move? (I want to know!)(6 votes)- You know how Earth is moving [rotating] Mars spins,moves too.(0 votes)
Why most people like to study the earth ?
What they are looking for?
Why do we live on earth?(4 votes)- Ok, those are some interesting questions, and I'll try my best to solve them.
Why do most people like to study earth?--
Well, I think a lot of people have realized earth is REALLY important, and people want to know about the planet that supported us for the past billion years. Also, just cause it's interesting, and we humans are known for our hunger for knowledge.
What are we looking for?--
Again, hunger for knowledge. Which means there is pretty much endless possibilities for studying and learning. Right now though, we are looking for another planet to shift to, because we have learned that our earth's resources are being used up.
Why do we live on Earth?--
We live on Earth because Earth was the lucky one and got the right distance from the sun, more resources, and life evolved here. We humans just happened to evolve as a life form on Earth.
Hope this helps!
;)(5 votes)
Isn't right now the space age?(3 votes)
Technically, the Space Age was considered to be the late 50s and the 60s when the Soviets are the U.S. engaged in a Space Race culminating when Apollo landed the first men on the moon.(4 votes)
is Mar's air breathable(3 votes)- Why does Mars and Earth tilt?(4 votes)
On the animation captioned: "Notice the temperature change based on the angle at which sunlight is hitting the Earth. Image: Peter Collingridge", what is the temperature scale?(4 votes)
Was Schiaparelli known for anything else(3 votes)
William Herschel used to look at Uranus and he wanted to call it "George star" because it moved so slow. then the name of Uranus was changed to the Greek god of the heavens and it also has moons. 27 orbit the planet the names comes from Shakespheare characters, the two large moons, Titania and Oberon were discovered and the names were suggested by his son John
Answer or Cancel Formatting tips(2 votes)