Astronomy

Why is the color of the moon so similar to the clouds?

Why is the color of the moon so similar to the clouds?


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Why the moon looks like the cloud-structure on the blue sky among the clouds?


The moon has dark and bright areas.

When it is visible in the daytime the bright areas appear roughly as bright as clouds, but the dark areas have no light to add to the scene and we are just left with the blue light from the sky generally.

The sky blue is not as bright as the clouds or the moon, at least when it's visible like this (typically near the end of day and early morning) so it does not conceal the bright clouds or the moon's brighter parts.


The Moon is a dark gray in color -- it reflects light poorly but uniformly. (Its color is about the same as fresh asphalt! It's albedo is about 12%) Clouds are (usually) light gray with an albedo ranging from 10% to 90%.

Both the Moon and the clouds shine by reflected sunlight, so they're both the same color. (Clouds usually have a greater surface brightness owing to their lower albedo.)


Sry Guys ;) english is not my main language so maybe i mesed in question :) still i think i found the answer , it serms everything on a blue sky would look cloudish ? My main concern was why moon looks more cloudish than clouds moonish ;) but now i think its just the contecst ;) Thx


What Color is the Moon?

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If the Moon’s up, go take a look and see what color it is. If you’re looking during the daylight, the Moon will look faint and white surrounded by the blue of the sky. If it’s night, the Moon will look bright yellow. Why does the color the Moon seem to change from white to yellow when you go from day to night. And why does the Moon look gray in many photographs, especially the ones from space? What color is the Moon?

The photographs of the Moon, taken from space are the best true-color views of the Moon. That gray color you see comes from the surface of the Moon which is mostly oxygen, silicon, magnesium, iron, calcium and aluminum. The lighter color rocks are usually plagioclase feldspar, while the darker rocks are pyroxene. Most of the rocks that you can see are volcanic, and were extruded from the inside of the Moon during volcanic eruptions. Some rare rocks called olivine are actually green.

The dark regions you see on the Moon are called lunar maria, and they were formed by ancient volcanic eruptions. They’re less reflective than the lunar highlands, and so they appear darker to the eye. The maria cover about 16% of the lunar surface, mostly on the side we can see from Earth. Astronomers think the lunar maria were formed about 3-3.5 billion years ago, when the Moon was much more volcanically active.

When you see the Moon from here on Earth, the atmosphere partially blocks your view. The particles in the atmosphere scatter certain wavelengths of light, and permit other wavelengths to get through directly. When the Moon is low in the sky, you’re seeing its light go through the most atmosphere. Light on the blue end of the spectrum is scattered away, while the red light isn’t scattered. This is why the Moon looks more red. As it goes higher in the sky, the Moon is obscured by less and less atmosphere, so it turns more yellow – the same thing happens to the Sun as it rises in the sky.

During the day, the Moon has to compete with sunlight, which is also being scattered by the atmosphere, so it looks white.

Here’s an article from Universe Today about harvest moons, and here’s an article about how astronomers calibrate photographs from space.

Here’s an article that explains how to get the right color of the Moon in Photoshop, and here’s an article from Windows on the Universe about the Moon’s colors in fall.

You can listen to a very interesting podcast about the formation of the Moon from Astronomy Cast, Episode 17: Where Did the Moon Come From?


Blood transfusion procedure

A blood transfusion is a straightforward procedure that a nurse carries out. At first, Donar will need to sign a consent form. Before blood transfusion, a nurse or doctor will go through with this. They can ask as many questions as they like. A nurse or doctor will take a small blood sample to check the blood type. It’s essential that donors are given blood that’s compatible with the receiver’s blood type. So donor must be correctly identified at each stage of the blood transfusion.

Then donor will be asked to state their full name and date of birth. Some people will be given a card when they have their blood transfusion to say that they can only get specific blood types.

Donar can be sitting up or lying down during transfusion and at roughly 15-minute intervals throughout the transfusion. The blood is usually given through a tiny tube called an intravenous line inserted directly into a vein in the arm using a fine needle. The insertion may cause slight discomfort for a moment, but the donor shouldn’t feel anything during the transfusion. It may take up to four hours to give the patient each bag of blood.

However, this can be safely speeded up when necessary or if it’s urgent. The patient may be given more than one bag of blood as part of your treatment. Blood transfusions are very safe, and it has many benefits. Donate your blood and save a life.


Titan's Mystery Clouds

This comparison of two views from NASA's Cassini spacecraft, taken fairly close together in time, illustrates a peculiar mystery: Why would clouds on Saturn's moon Titan be visible in some images, but not in others?

In the top view, a near-infrared image from Cassini's imaging cameras, the skies above Saturn's moon Titan look relatively cloud free. But in the bottom view, at longer infrared wavelengths, Cassini sees a large field of bright clouds. Even though these views were taken at different wavelengths, researchers would expect at least a hint of the clouds to show up in the upper image. Thus they have been trying to understand what's behind the difference.

As northern summer approaches on Titan, atmospheric models have predicted that clouds will become more common at high northern latitudes, similar to what was observed at high southern latitudes during Titan's late southern summer in 2004. Cassini's Imaging Science Subsystem (ISS) and Visual and Infrared Mapping Spectrometer (VIMS) teams have been observing Titan to document changes in weather patterns as the seasons change, and there is particular interest in following the onset of clouds in the north polar region where Titan's lakes and seas are concentrated.

Cassini's "T120" and "T121" flybys of Titan, on June 7 and July 25, 2016, respectively, provided views of high northern latitudes over extended time periods -- more than 24 hours during both flybys. Intriguingly, the ISS and VIMS observations appear strikingly different from each other. In the ISS observations (monochrome image at top), surface features are easily identifiable and only a few small, isolated clouds were detected. In contrast, the VIMS observations (color image at bottom) suggest widespread cloud cover during both flybys. The observations were made over the same time period, so differences in illumination geometry or changes in the clouds themselves are unlikely to be the cause for the apparent discrepancy: VIMS shows persistent atmospheric features over the entire observation period and ISS consistently detects surface features with just a few localized clouds.

The answer to what could be causing the discrepancy appears to lie with Titan's hazy atmosphere, which is much easier to see through at the longer infrared wavelengths that VIMS is sensitive to (up to 5 microns) than at the shorter, near-infrared wavelength used by ISS to image Titan's surface and lower atmosphere (0.94 microns). High, thin cirrus clouds that are optically thicker than the atmospheric haze at longer wavelengths, but optically thinner than the haze at the shorter wavelength of the ISS observations, could be detected by VIMS and simultaneously lost in the haze to ISS -- similar to trying to see a thin cloud layer on a hazy day on Earth. This phenomenon has not been seen again since July 2016, but Cassini has several more opportunities to observe Titan over the last months of the mission in 2017, and scientists will be watching to see if and how the weather changes.

These two images were taken as part of the T120 flyby on June 7 (VIMS) and 8 (ISS), 2016. The distance to Titan was about 28,000 miles (45,000 kilometers) for the VIMS image and about 398,000 miles (640,000 kilometers) for the ISS image. The VIMS image has been processed to enhance the visibility of the clouds in this false-color view, clouds appear nearly white, atmospheric haze is pink, and surface areas would appear green.

The Cassini mission is a cooperative project of NASA, ESA (the European Space Agency) and the Italian Space Agency. The Jet Propulsion Laboratory, a division of Caltech in Pasadena, California, manages the mission for NASA's Science Mission Directorate, Washington. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colorado. The visual and infrared mapping spectrometer team is based at the University of Arizona.


The Moon's Two Sides Look So Different Thanks To 4.5 Billion-Year-Old Physics

If you’ve ever looked up at the brightest and closest celestial object in the night sky, our Moon, you’ve probably noticed how different some parts of it appear to be from others. And if you’ve ever taken a look at it through a telescope, especially if it’s not in its full phase, you’ve very likely noticed some remarkable features on its surface.

Image credit: Gregory H. Revera, via Wikimedia Commons from . [+] http://en.wikipedia.org/wiki/File:FullMoon2010.jpg.

In particular, there are two main features that even a casual visual inspection will reveal:

  1. That it’s heavily cratered, especially in the lighter-colored areas. Many cratered regions include small craters inside medium-sized craters inside giant craters. And…
  2. That it has these large areas that are much darker than the rest, known as maria (latin for “seas”), which have relatively few and mostly smaller craters in them. These regions are notable for being a significantly different color/reflectivity than the majority of the Moon.

The same side of the Moon always faces us, but different portions of the lunar hemisphere get illuminated throughout the month, dependent on the relative positions of the Earth, Moon and Sun.

In addition, because the Moon’s orbit is elliptical, moving faster when it’s closest to Earth and slower when it’s farthest away, the face of the Moon that’s visible changes ever-so-slightly, a phenomenon known as lunar libration. Even though this means, over the course of many months, we could see up to a total of 59% of the Moon, it wasn’t until 55 years ago, when the Soviet spacecraft Luna 3 swung around to the far side of the Moon, that we were finally able to see the full 100% of the surface.

Although it wasn’t very impressive, many subsequent pictures have shown us what the side facing away from Earth actually looks like, and it should come as quite a shock!

Image credit: NASA / JPL-Caltech / LRO.

It's so different! One thing you’ll notice right away is the almost complete absence of the dark maria on the far side, and perhaps the second thing you’ll see is how much more prominently and thoroughly cratered the far side is.

Although this was first discovered all the way back in 1959, it took a lot longer to come up with a reason for this mystery. You see, there’s an obvious explanation — that perhaps you even thought of yourself — but it turns out to be wrong.

Image credit: ESA / P. Caril.

The Solar System is full of hazardous comets and asteroids, periodically plunging into the inner regions where the rocky planets are. When things go well for the inner worlds, these bodies produce spectacular displays like cometary tails and meteor showers. But when things go poorly, one of those large bodies smacks into a larger one, creating a catastrophic impact!

The “obvious” explanation would be that when these massive space rocks head towards the Moon from the far side, there’s nothing at all getting in the way. But when you approach the Moon from the near side, the Earth is in the way, and that it can either absorb those impacts or gravitationally deflect those potential impactors away from the Moon.

It’s a nice idea, but the fact that the Earth-Moon distance is some thirty times larger than the diameter of the Earth means that the difference in the number of impacts on the near side of the Moon from the far side ought to be less than 1% when we run the numbers. The answer, it turns out, does have something to do with space collisions, but not like you’re thinking!

Image credit: NASA/JPL-Caltech.

You might think the asteroid that wiped out the dinosaurs was a big one, and compared to the other collisions that have happened in the past 100 million years, it was. Roughly 5-to-10 km across, that mass extinction causing asteroid was the size of a very large mountain. But it's not the largest collision in Earth’s history, not by a long shot. We didn’t even realize this until we brought rocks back from the Moon, and discovered that they’re made of exactly the same stuff as Earth is made out of! This was a big surprise, because no other moon/planet companions in the Solar System — not Jupiter and its moons, not Mars and its Moons, not Saturn and its Moons — are like that. How did this come to be?

Some 4.5 billion years ago, when the Solar System was still in its infancy, the Earth was mostly formed, and was around 90-96% of its present mass. But there was another very large, Mars-sized planetoid that was in an almost identical orbit to Earth’s. For tens of millions of years, these two objects unstably danced away from one another. And then, finally, they collided with one another!

Image credit: H.Seldon, released into the public domain.

The vast majority of both proto-planets wound up forming the Earth, while a large amount of debris was kicked up into space. Over time, this debris coalesced gravitationally to form the Moon! As crazy as it sounded when it was proposed in the 1970s, this has come to be the accepted theory — verified by many observable phenomena that match the predictions — over the past 40 years.

Now, this collision happened very early in the Solar System’s history, and the Earth was still very hot when it happened: around 2,700 Kelvin! The Moon might have been much closer, but was still tens of thousands of kilometers away. Even so, having that extra heat source close by — and having the Moon already be tidally locked (with one side always facing us) — meant that the near side of the Moon was going to be much hotter for a very long time than the far side would be!

Image credit: NASA's Goddard Space Flight Center Conceptual Image Lab, of the (hot) early Earth.

The maria that we see are evidence of lava flows, where molten rock flowed into the great basins. While the far side of the Moon cooled relatively quickly and formed a thick crust, the large temperature gradient caused by being in close proximity to Earth on the near side left huge amounts of the near side in the liquid state for longer, giving it far less time to have the effects of impacts leave features on the surface. Just like meteors striking the Earth’s oceans, the ones landing in the Moon’s ancient lava oceans didn’t leave scars!

It was only in June of this year that a study by Arpita Roy, Jason Wright and Steinn Sigurdsson appeared to have figured this all out and presented the necessary evidence to support it . They created a model of the early Earth-Moon system and showed that simply by having a hot Earth near enough to a tidally locked Moon — just by adding that one-sided heat source — it could create the crustal difference and the elemental, chemical difference between the two sides. It explains why the far side contains lunar highlands, while the near side contains these intense maria.

Images credit: NASA / JPL-Caltech / LRO.

And so, for the first time, we can confidently state not only how the Moon formed, but why the two sides are so different! We know that the Moon shines by reflecting the Sun’s light, but who would’ve imagined that it was the young Earth, glowing bright and hot in the Moon’s sky, that would make the two sides so different? That’s just part of the wonder and joy of science!


Icy clouds could have kept early Mars warm enough for rivers and lakes

One of the great mysteries of modern space science is neatly summed up by the view from NASA's Perseverance, which just landed on Mars: Today it's a desert planet, and yet the rover is sitting right next to an ancient river delta.

The apparent contradiction has puzzled scientists for decades, especially because at the same time that Mars had flowing rivers, it was getting less than a third as much sunshine as we enjoy today on Earth.

But a new study led by University of Chicago planetary scientist Edwin Kite, an assistant professor of geophysical sciences and an expert on climates of other worlds, uses a computer model to put forth a promising explanation: Mars could have had a thin layer of icy, high-altitude clouds that caused a greenhouse effect.

"There's been an embarrassing disconnect between our evidence, and our ability to explain it in terms of physics and chemistry," said Kite. "This hypothesis goes a long way toward closing that gap."

Of the multiple explanations scientists had previously put forward, none have ever quite worked. For example, some suggested that a collision from a huge asteroid could have released enough kinetic energy to warm the planet. But other calculations showed this effect would only last for a year or two -- and the tracks of ancient rivers and lakes show that the warming likely persisted for at least hundreds of years.

Kite and his colleagues wanted to revisit an alternate explanation: High-altitude clouds, like cirrus on Earth. Even a small amount of clouds in the atmosphere can significantly raise a planet's temperature, a greenhouse effect similar to carbon dioxide in the atmosphere.

The idea had first been proposed in 2013, but it had largely been set aside because, Kite said, "It was argued that it would only work if the clouds had implausible properties." For example, the models suggested that water would have to linger for a long time in the atmosphere -- much longer than it typically does on Earth -- so the whole prospect seemed unlikely.

Using a 3D model of the entire planet's atmosphere, Kite and his team went to work. The missing piece, they found, was the amount of ice on the ground. If there was ice covering large portions of Mars, that would create surface humidity that favors low-altitude clouds, which aren't thought to warm planets very much (or can even cool them, because clouds reflect sunlight away from the planet.)

But if there are only patches of ice, such as at the poles and at the tops of mountains, the air on the ground becomes much drier. Those conditions favor a high layer of clouds -- clouds that tend to warm planets more easily.

The model results showed that scientists may have to discard some crucial assumptions based on our own particular planet.

"In the model, these clouds behave in a very un-Earth-like way," said Kite. "Building models on Earth-based intuition just won't work, because this is not at all similar to Earth's water cycle, which moves water quickly between the atmosphere and the surface."

Here on Earth, where water covers almost three-quarters of the surface, water moves quickly and unevenly between ocean and atmosphere and land -- moving in swirls and eddies that mean some places are mostly dry (the Sahara) and others are drenched (the Amazon). In contrast, even at the peak of its habitability, Mars had much less water on its surface. When water vapor winds up in the atmosphere, in Kite's model, it lingers.

"Our model suggests that once water moved into the early Martian atmosphere, it would stay there for quite a long time -- closer to a year -- and that creates the conditions for long-lived high-altitude clouds," said Kite.

NASA's newly landed Perseverance rover should be able to test this idea in multiple ways, too, such as by analyzing pebbles to reconstruct past atmospheric pressure on Mars.

Understanding the full story of how Mars gained and lost its warmth and atmosphere can help inform the search for other habitable worlds, the scientists said.

"Mars is important because it's the only planet we know of that had the ability to support life -- and then lost it," Kite said. "Earth's long-term climate stability is remarkable. We want to understand all the ways in which a planet's long-term climate stability can break down -- and all of the ways (not just Earth's way) that it can be maintained. This quest defines the new field of comparative planetary habitability."

The co-authors on the paper were former UChicago postdoctoral researcher Liam Steele, now with the Jet Propulsion Laboratory Michael Mischna of the Jet Propulsion Laboratory, and Mark Richardson of Aeolis Research. Parts of the analysis were performed at the University of Chicago Research Computing Center.


Sunset clouds

Although clouds are composed of ice and water droplets, they don't appear white or transparent as water does either in a liquid or frozen form. This is because a cloud is composed of billions of tiny water droplets or ice crystals they act like billions of reflective glass beads, which are very effective in scattering sunlight, producing a white color.

And since they are excellent reflectors, clouds can appear to take on a variety of colors: yellow, orange, red or even pink around the time of sunrise or sunset. Blot out the sun and a backlit cloud can appear uniformly gray or even black.

In his very popular "Weather Book," the late Eric Sloane points out that the most magnificent sunset colors often are not in the direction of the setting sun in the west, but in the east:

&ldquoWhen you are in the open and viewing the sun going down, do watch the deep and sullen clouds on the opposite eastern horizon as they reflect the setting western light. The changing colors are as thrilling as a symphony.&rdquo [Image Gallery: Sunrises and Sunsets]


Nacreous Clouds

To see a nacreous or polar stratospheric cloud, you'll have to do more than simply look up. In fact, you'll need to travel up to the world's farthest polar regions and visit the Arctic (or Antarctica in the Southern Hemisphere).

Taking their name from their "mother of pearl"-like appearance, nacreous clouds are rare clouds that only form in the extreme cold of the polar winter, high up in Earth's stratosphere. (The stratosphere's air is so dry, clouds can only form when temperatures are extremely cold, as in -100 F cold!) Given their high altitude, these clouds actually receive sunlight from below the horizon, which they reflect to the ground at dawn and just after dusk. The sunlight within them undergoes forward-scattering towards sky watchers on the ground, making the clouds appear a bright pearly-white while at the same time, the particles within the thin clouds diffract the sunlight and cause iridescent highlights.

But don't be fooled by their whimsy—as spectacular as nacreous clouds appear, their presence allows for the not-so-nice chemical reactions that lead to ozone depletion.


Watch the video: What Color Is The Moon? (November 2022).