Mars 1971
Telescopic views of Mars (above) show the varying size of the south polar cap.
The Southern Hemisphere of Mars experiences late spring and summer when the planet is at (or near) perihelion. In other words, in the south, the warmth resulting from being tilted toward the sun is compounded by the planet's relative nearness to the sun. Relatively warm conditions, and the midnight sun, causes the polar cap to shrink rapidly. The sublimation of frozen CO2 leads to high pressure in the south polar region. The gas shoots northward to fill the partial vacuum of the rest of the planet. High wind velocity, coupled with the low gravity of Mars, stirs up great quantities of dust, leading to the legendary dust storms.
In 1971, Mars was at perihelion on September 8. Not surprisingly, a dust storm broke out around then, and soon encompassed the entire planet. This was disadvantageous for the US Mariner 9 spacecraft. Launched in May 1971, it began orbiting Mars in November for the purpose of mapping that world. Initially, a dusty atmosphere obscured the Martian surface.
The dust gradually settled, revealing many interesting features on Mars, including its huge volcanoes.
First seen in 1971, Nix Olympica is the largest volcano in the solar system. Mars also has the Vallis Marineris, a big canyon complex named after the spacecraft which detected it.
posted by starman at 4:30 AM
31 Comments:
That dust storm on Mars was larger than any that have occurred on Earth. The volcano in one of those photos must have spewed out ash that encircle the whole planet.
Besides the ash, there were lava flows that covered vast areas on Mars. The Amazonis region is an example. It is relatively young because the lava buried the older, cratered surface.
March 9, 2021
From what I've read, the lower gravity enables lava to flow longer and over an extremely widespread area.
Sure, lower gravity makes it easier for lava to rise to the surface, and flow. Interestingly, though, Roger Skutt (whom I haven't heard from since 2016) wrote that high gravity is conducive to volcanism, since the underground lava is squeezed out.
Btw Neal, do you remember Mariner 9? This year marks the 50th anniversary of that mission, which taught humanity more about Mars than it had known in all the time it had been around prior to '71.
March 10, 2021
I remember Mariner 9. You're right, it provided a lot of data about Mars that had not been known. Some people have brought forth the idea that Mars had life in the past. There are those who say that volcanic activity could have wiped out life on Mars if it existed there.
I doubt volcanic activity sterilized Mars; the planet was already inhospitable long before the biggest eruptions. Mariner 9 photos showed evidence of flowing water, giving rise to the idea of a "warm, wet" Martian epoch but see Carr WATER ON MARS for a different view.
Btw did you hear about Brandenburg's book DEATH ON MARS? He thinks aliens nuked the red planet and wiped out an indigenous civilization there. That's absurd.
March 11, 2021
I haven't read Brandenburg's book, but I agree, his idea is ridiculous. If a civilization would have existed on Mars, probes would have made photographs of evidence, for example, architectural structures.
Since 1976, when the Mars "face" was discovered, there have been claims of architectural structures but they're unconvincing to say the least. It's hard to believe Brandenburg or any reputable scientist believes there are/were intelligent Martians. One old UFO book stated it pretty well: "While UFO aliens may have built a spaceport on Mars, it is inconceivable the red planet harbors an indigenous civilization." Mars appears too inhospitable for microbes let alone advanced life.
March 12, 2021
I agree, the idea of an indigenous civilization seems too far fetched. I can see how UFO aliens could have built a spaceport there. The conditions for constructing a port are better on Mars than they are on most planets in this solar system. It is very likely that they have visited Mars.
Agreed, it's virtually certain UFO aliens know about Mars even if they aren't from the red planet. I think, though, their bases are here on Earth, underground or under the sea. Assuming they need bases and can't zip instantaneously from their original home to Earth.
March 13, 2021
I agree, Mars is feasible, but Earth has an environment that is more hospitable to having bases. Venus is so hot that any landing on it would melt. I don't think that bases could be put on Uranus, Neptune, or Jupiter. UFO aliens have obviously figured out how to get around the speed of light. I don't know how they do it, but I have heard some theories. One is that there is an alternate universe in which nothing goes below the speed of light. Some people have suggested that UFO alien starships enter that zone and go far beyond the speed of light for a while before re-entering this universe. I am not assuming that the theory is correct. However, it is something that is interesting to consider.
Some time ago on the paracast forum a guy surnamed Morrison opined that UFOs travel by means of Gravitational Field Propulsion. It has no time dilation effect. I'm not a physics expert and so can't comment much on the proposed methods. It does appear obvious, though, that the speed of light does not impede interstellar travel.
Btw that article you posted in fb, about Martian dust being the source of the zodiacal light, was very interesting. I assume impacts must have blown considerable dust, as well as rocks, into space. Surely Martian winds, despite their occasional high velocity, can't get dust particles to reach escape velocity.
March 14, 2021
It's an odd issue. It seems improbable that Martian winds could not enable dust particles to reach escape velocity. I am wondering if some additional unknown factors might be at work.
I winder if the solar wind could blow dust particles into space, just as it occasionally causes Mars to lose gases. I doubt it though. Impacts seem by far the best explanation, and some past impacts were VERY big.
March 15, 2021
I am guessing some of those impacts were much harder than any made by meteors that hit Earth.
Impacts on Mars weren't necessarily bigger than any that struck Earth, but big enough to create the Hellas and Argyre basins. In fact much of the Northern hemisphere of Mars is thought to represent a vast impact crater. No doubt impacts of that magnitude ejected dust, as well as rocks, into space (causing the zodiacal light).
March 16, 2021
Some of the craters on Mars are over 400 km. in diameter. For example, the Huygens crater has a diameter of 467.25 km. That crater was discovered in 1973. It was named after Christian Huygens.
Huygens crater is in fact small compared to Argyre planitia, and Hellas. Argyre is 1,800 kilometers or about 1,100 miles across. Hellas is even larger and deeper. It's hard to believe the enormous impacts which formed these structures failed to kick dust into interplanetary space near Mars.
March 17, 2021
It seems to me that most likely some of them would have put some dust into interplanetary space close to that planet. Argyre and Hellas certainly must have done that. I think that Huygens crater also did it, though to a lesser extent.
Considering that these dust-ejecting impacts occurred billions of years ago, the zodiacal light has probably existed since the early history of the solar system.
Btw Neal, when did you first see and recognize Mars in the night sky? I definitely saw it in May 1971, though I might have done so in 1969.
March 18, 2021
I first saw it in the night sky in July of 1969. My dad had his telescope out in the yard and we looked through it. I plan to get a look at Mars soon through my telescope.
July of '69 was a good time to see Mars. It was a couple of months past opposition but well up from the horizon earlier after sundown. I noted the same thing in late August 1971, after Mars had passed opposition.
Btw do you remember when you first saw Mercury?
March 20, 2021
I might have seen Mars in the summer of 1969 even if I didn't yet recognize it. At the time I became curious about the night sky and wished I knew more so I could identity things. (It is possible I saw and recognized Mars in December 1969 when it appeared near the moon, but I'm not sure.) I learned the constellations and saw the five most conspicuous planets in 1970-71.
March 20, 2021
Yes, I got my first look at Mercury in the summer of 1964, shortly after a I finished the 5th grade. As we know, that planet does not have moons. In February of 1971, I saw Jupiter through my dad's telescope. That telescope was strong enough for us to see three moons of it.
You sure saw Mercury at an earlier age than I did. I didn't see it until March 1972. When in the summer of '64 did you see Mercury? I've seen it in June, but it becomes harder to see in July and August, in the evening sky, because the ecliptic becomes lower in the western sky after sundown. Did your father point out Mercury to you?
I first saw Jupiter's moons and Saturn's rings in 1973-74, after I got a 60mm refractor.
March 22, 2021
I saw it in June of 1964. My father pointed it out to me. From what I've read, Mercury is not as hot as Venus, even though Mercury is closer to the sun. Most of the atmosphere of Mercury consists of carbon dioxide, along with some other gases, such as methane.
This is all very interesting; I do not have the scientific background to understand much of it, but I enjoyed reading about when people were able to see various planets. I did see the rings of Saturn once, on an outing to the top of a hill sponsored by an astronomy club. They let us look through their powerful telescopes.
I suspected you saw Mercury in June. That's about the only time in the summer when Mercury can be seen in the evening sky. After the summer solstice the ecliptic sinks rapidly i.e. when seen in the western sky after sundown.
True Mercury doesn't have an atmosphere hence doesn't have a greenhouse effect which in the case of Venus became a runaway greenhouse effect. The atmosphere of Venus is mainly CO2 and sulfur dioxide.
Welcome NewBlogger, hope to see you often here! How big a telescope did the club have? I've seen the rings of Saturn with 60mm and 90mm refractors and 6 and ten inch reflectors.
March 23, 2021
At least 15 impact craters have been identified on Mercury. The largest is the Caloris Basin. It has a diameter of 1550 km. (963.1 miles). When the impact took places, lava eruptions occurred. A concentric ring over 2 km. (1.2 mi.) in height is around the crater.
I've heard of the Caloris basin. The name caloris alludes to the intense heat of Mercury.
March 26, 2021
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