Guide to Space Archives

December 1, 2009December 24, 2015 by Fraser Cain

Mars Exploration Rover

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One of the most successful mission ever sent to Mars is the Mars Exploration Rover program, with the two rovers Spirit and Opportunity. They were launched separately to Mars in 2003 and landed safely several months later. They were supposed to last about 3 months on the surface of Mars, but have now survived more than 5 years.

Spirit and Opportunity used technology developed with the Mars Pathfinder mission. They used an airbag system to land on the surface of Mars without using retrorockets to touch down gently. They also use the rover technology first used with the Sojourner rover, but instead of operating from a base, Spirit and Opportunity were designed to be completely independent, able to communicate directly back to Earth.

The purpose of the Mars Exploration Rover mission (MER) was to search the surface of Mars for evidence of past water on the surface of Mars. Spirit landed in the huge Gusev Crater on Mars, a region that could have been an ancient lake on Mars. Opportunity touched down on the other side of the planet in a region called Meridiani Planum.

Both Spirit and Opportunity are equipped with solar panels that supply electricity to let them crawl around the surface of Mars, as well as their scientific instruments that let them study the surface of Mars and its rocks. They’re also equipped with a grinding tool that lets them scrape away the outer layer of rocks and see the material underneath.

Within just a few months of arriving on Mars, both Spirit and Opportunity fulfilled their mission objectives, and discovered evidence that large quantities of water used to be on the surface of Mars. Spirit discovered hints that water had acted on a rock called Humphrey, while Opportunity found layers of sedimentary rock that would have been formed by deposits in water. Both rovers continued to find additional evidence for the presence of water.

Over the course of their mission on the surface of Mars, both rover traveled several kilometers. Spirit climbed a small mountain, and Opportunity crawled into a large crater to sample the walls for evidence of past water. And both rovers continued to perform quite well, for many years beyond their original estimate life spans.

We have written many articles about the Mars Exploration Rovers for Universe Today. Here’s an article about the troubles for the Spirit rover, and here’s an article about Martian weather.

If you’d like more info on the rovers, you should check out the Mars Exploration Rover homepage from NASA.

We’ve also recorded several episodes of Astronomy Cast about the exploration of Mars. Start here, Episode 92: Missions to Mars, Part 1.

Source: NASA

December 1, 2009December 24, 2015 by Fraser Cain

Mars Pathfinder

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Mars Pathfinder was NASA mission to Mars, which launched on December 4th, 1996 and landed on the surface of Mars on July 4, 1997. Unlike the missions that went before it, the Pathfinder lander was also equipped with a tiny rover called Sojourner, which could venture away from the lander, crawl around the surface of Mars and study rocks up close. It was a relatively inexpensive mission that tested out many of the technologies build into later missions, like the Mars Exploration rovers Spirit and Opportunity.

The purpose of Pathfinder was to prove that the concept of “faster, better and cheaper” missions would work. Pathfinder only cost $150 million and was developed in under 3 years. It was also sent to study the surface of Mars, including the geochemistry of the rocks, the magnetic properties of the surface and the structure of the planet’s atmosphere.

When the Pathfinder mission arrived at Mars, it entered the atmosphere and deployed a parachute. Instead of using retrorockets to land gently on the surface, however, Pathfinder used an airbag system. This allowed it to save fuel; instead of landing gently, it was dropped from an altitude of about 100 meters onto the Martian surface. It bounced several times and came to a rest before opening up like the petals of a flower. Once everything checked out, the tiny Sojourner Rover was deployed onto the surface of Mars.

The area around the Pathfinder site had many rocks, large and small, and the NASA scientists gave them unique names like “Barnacle Bill” and “Yogi”. Sojourner was able to crawl around and study these rocks up close. It was able to study the chemical makeup of the rocks, and confirmed that they formed from past volcanic activity. Over the course of the entire mission, Pathfinder and Sojourner returned 16,500 images and made millions of measurements of the Martian atmosphere.

Pathfinder stopped communicating with Earth after 83 days on the surface of Mars. Its battery was only designed to be recharged 40 times, and once its battery stopped working, the spacecraft was unable to keep its electronics heated in the cold Martian night. After it stopped communicating, NASA decided to name the lander after Carl Sagan. It became The Carl Sagan Memorial Station.

We have written many articles abut the Mars Pathfinder mission for Universe Today. Here’s an article about photos of Mars Pathfinder taken from orbit, and research about a cold and wet early Mars.

Here’s a link to the original mission homepage for the Mars Pathfinder.

We’ve recorded several episodes of Astronomy Cast about missions to Mars. Start here, Episode 92: Missions to Mars, Part 1.

Source: NASA

November 30, 2009December 24, 2015 by Fraser Cain

What Color is Venus?

Venus. Image Credit: NASA/courtesy of nasaimages.org

Here’s a question: what color is Venus? With the unaided eye, Venus just looks like a very bright star in the sky. But spacecraft have sent back images of the cloud tops of Venus, and some have even returned images from the surface of Venus.

If you could actually fly out to Venus and look at it with your own eyes, you wouldn’t see much more than a bright white-yellowish ball with no features. You wouldn’t actually be able to see any of the cloud features that you can see in photographs of Venus. That’s because those photos are taken using different wavelengths of light, where differences in the cloud layers are visible. For example, the photo that accompanies this story was captured in the ultraviolet spectrum.

Although the atmosphere of Venus is almost entirely made up of carbon dioxide, the clouds that obscure our view to the surface are made of sulfur dioxide. These are opaque to visible light, and so we can’t see through them to the surface of Venus. These clouds actually rain droplets of sulfuric acid.

If you could get down beneath the cloud tops of Venus, you wouldn’t be able to see much either. That’s because the clouds are so thick that most of the light from the Sun is blocked before it reaches the surface. You would see a dim landscape, like you might see at twilight. The surface of the planet is littered with brownish-red volcanic rocks. The bright red color you see in the Soviet Venera images of Venus have been brightened to show more surface detail.

So, what color is Venus? Yellowish-white.

We’ve written several articles about the color of the planets for Universe Today. Here’s an article about the color of Mercury, and here’s an article about the color of Pluto.

If you’d like more info on Venus, check out Hubblesite’s News Releases about Venus, and here’s a link to NASA’s Solar System Exploration Guide on Venus.

We’ve also recorded an entire episode of Astronomy Cast all about Venus. Listen here, Episode 50: Venus.

November 27, 2009May 4, 2017 by Fraser Cain

Who Discovered Saturn?

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Were you wondering who discovered Saturn? Well, nobody knows. Here’s the problem. Saturn is one of the 5 planets that you can see with the unaided eye. In fact, if you’re seeing a bright star in the sky, there’s a good chance it’s Saturn. It takes a telescope to see the rings, but anybody can find Saturn, even in a bright city.

So perhaps a better question might be to ask, when did astronomers realize that Saturn was a planet? The ancient astronomers believed in the geocentric model of the Universe. The Earth was at the center of the Universe, and everything else orbited around it in crystal shells: the Sun, the Moon, the planets and the stars. One problem with this model was the strange movements of the planets. They would sometimes slow down, stop and even travel backwards in the sky. And to explain this, astronomers had to create elaborate models for the planets where the orbited inside spheres within spheres.

Anyway, this model was turned on its ear by Nicolaus Copernicus in the 1500s. He placed the Sun at the center of the Solar System, and had all the planets orbiting around it. This nicely explained the strange movements of the planets. They weren’t going backwards, it was just a change in perspective, since the Earth is also going around the Sun.

The first person to actually look at Saturn in a telescope was Galileo. He saw a strange oval-shaped planet. He thought the planet might have ears, or two small balls on either side. Later observations showed that these were actually Saturn’s grand ring system. Galileo also discovered Saturn’s moon Titan.

Better observations of Saturn by Giovanni Cassini turned up 4 additional moons of Saturn, as well a division in the rings that would later be named after him: the Cassini division.

But it wouldn’t be until 1979 that the first spacecraft flew past Saturn. NASA’s Pioneer 11 spacecraft made the journey, getting within 20,000 km of the planet’s cloud tops. This was followed by the Voyager spacecraft, and eventually NASA’s Cassini spacecraft that’s orbiting the planet today. All of our best images of Saturn were sent back by orbiting spacecraft.

We have written many articles about the discovery of planets for Universe Today. Here’s an article about the discovery of Uranus, and here’s an article about the discovery of Neptune.

If you’d like more info on Saturn, start with the NASA Cassini mission homepage. That’s where you’ll see all the latest news and photos sent back from Saturn. Then check out Hubblesite’s News Releases about Saturn.

We’ve also recorded an entire episode of Astronomy Cast just about Saturn. Check it out here, Episode 59: Saturn.

Reference:
NASA

November 27, 2009December 24, 2015 by Fraser Cain

When Was Venus Discovered?

Were you wondering when was Venus discovered? Actually, there’s no way to know. Venus is one of the 5 planets visible with the unaided eye. In fact, Venus is the brightest object in the night sky after the Sun and the Moon. When Venus is at its brightest, it even casts shadows. So even ancient people would have been aware of Venus, and so there’s no way to know who that first person was, and when it happened.

However, a better question might be to ask, when did we know that Venus was a planet? This happened about the same time that astronomers first realized the Earth was a planet too. In ancient times, astronomers used to think that the Earth was the center of the Universe, and everything orbited around it: the Sun, the Moon, the planets and the stars. One problem with this model was the strange behavior of the planets. Sometimes they would speed up, and then slow down, stop, and even go backwards in the sky.

But then in the 1500s, Nicolaus Copernicus developed his model of a Sun-centered Solar System. The Earth was just a planet, and all of the planets orbited around the Sun instead. This model explained how the planets could have such strange movements. Since the Earth is moving too, we’re really just seeing them from different perspective in they sky.

The first person to see Venus in a telescope was Galileo. Although he wasn’t able to resolve anything but a bright disk (astronomers can’t do any better today), he saw that Venus went through phases like the Moon. This was further evidence that Venus orbits around the Sun – closer than the Earth, and so we see it in various phases of illumination.

Because Venus is shrouded in clouds, astronomers weren’t able to get a better view of Venus until the first spacecraft arrived from Earth. The first spacecraft to visit Venus was NASA’s Mariner 2, which arrived at Venus in 1962. But even then the planet was still blocked by clouds. The Russian Venera landers were able to pierce through the clouds and landed on the surface to send back a few quick images of the planet’s surface. They showed a hellish world, with thick atmosphere, clogging clouds, and blasting heat, hot enough to melt lead. NASA’s Magellan spacecraft (launched in 1989) was equipped with a radar instrument that allowed it to pierce through the clouds on Venus and show the planet’s landscape, craters and volcanoes.

We’ve written many articles about the discovery of planets for Universe Today. Here’s an article about the discovery of Uranus, and here’s an article about the discovery of Neptune.

If you’d like more information on Venus, check out Hubblesite’s News Releases about Venus, and here’s a link to NASA’s Solar System Exploration Guide on Venus.

We’ve also recorded an entire episode of Astronomy Cast about Venus. Listen here, Episode 50: Venus.

November 27, 2009December 24, 2015 by Fraser Cain

Who Discovered Mars?

Mars is one of the 5 planets visible with the unaided eye. On any dark night, when Mars is in the sky, it’s easy to see with your own eyes. Ancient people knew about Mars, and long ago discovered that it moves from night to night compared to the stars. So it’s impossible to know who discovered Mars. That would have been one of the first humans.

Perhaps a better question to ask is: who realized that Mars is a planet? And that discovery happened with the idea that the Earth is a planet.

In ancient times, astronomers thought that the Earth was the center of the Universe, and the Sun, Moon, planets and stars orbited around us in a set of crystalline spheres. But the motions of the planets were hard to explain; they would sometimes speed up, stop, and even reverse their direction in the sky.

But the astronomer Nicolaus Copernicus developed the view that it was the Sun that was at the center of the Solar System, and the planets orbited around it. This view neatly explained the strange motions of the planets, since the Earth was also moving around the Sun, and these quirks were really just changes in perception.

Galileo was the first person to view Mars in a telescope, and he saw not much more than a bright disk. He did take many observations over the course of the year and realized that Mars gets closer and more distant, and so larger and smaller in his telescope. As telescopes got bigger and better, astronomers were able to make out the polar ice caps on Mars, and some astronomers incorrectly thought they saw a system of canals crisscrossing the surface of the planet.

But the best views of Mars came with the first robotic exploration of Mars. The first spacecraft to arrive at Mars was NASA’s Mariner 4, launched in 1964. The first spacecraft to go into orbit around Mars was Mariner 9, in 1971. These spacecraft helped take high resolution images that revealed craters, mountains and chasms; the red landscape of Mars that we’re so familiar with today.

We’ve written many articles about the discovery of planets for Universe Today. Here’s an article about the discovery of Uranus, and another about the discovery of Neptune.

If you’d like more information on Mars, check out Hubblesite’s News Releases about Mars, and here’s a link to the NASA Mars Exploration home page.

We’ve also recorded several episodes of Astronomy Cast about Mars. Start here, Episode 52: Mars.

References:
NASA Mars Exploration
NASA: The Mariner Missions

November 25, 2009April 26, 2016 by Abby Cessna

Yellowstone National Park Volcano

Artist's impression of a what lies beneath the Yellowstone volcano. Credit: Hernán Cañellas/National Geographic

Yellowstone National Park is known for its geysers, but did you know that it is also the site of one of the world’s largest volcanoes? The same geologic activity that causes the multitude of geysers in the park is also responsible for the huge volcano located there. Scientists estimate that it is one of the largest volcanoes in the world, and so far it is the largest volcano in North America.

The volcano is 55 km by 72 km in size. Yellowstone’s volcano is in the class of super volcanoes due to its size. There is no exact definition for what qualifies as a super volcano; however, some scientists have defined it as a volcano with an eruption greater than 240 cubic miles.

Additionally, the Yellowstone Volcano does not look like the popular image of a volcano. Instead of being a conical mountain, it is a large depression in the ground like a cauldron. This type of volcanic feature is known as a caldera. It is very difficult to see the actual shape because it is covered with trees and has eroded over thousands of years.

*Yellowstone National Park sits on top of a giant volcanic caldera, or an earthen cap that covers a huge reservoir of superhot liquid rock and poison gasses. Credit: IO9*

The cause of the volcano is the hotspot on which Yellowstone is located. At a hotspot, molten mantle rock tends to rise toward the surface causing different geological activity. Volcanic eruptions from the hotspot also helped form the Snake River Plain.

Not only do volcanic eruptions occur around the Yellowstone region, but the area also experiences many earthquakes. The region experiences around 1000 to 2000 earthquakes each year, although most of them are usually quite small.

Despite the fact that the volcano has not erupted in hundreds of years, it is still active. This is a concern to scientists who have placed sensors around Yellowstone, so the volcano is continually monitored. The possible eruption of the Yellowstone Super volcano is of concern because of the enormous destruction it would cause. The last eruption was believed to be approximately 640,000 years ago.

Geologists estimate that 2 million years ago a cataclysmic series of volcanic eruptions in the Yellowsone Caldera was 2,500 times more powerful than the Mt. St. Helens eruption and perhaps was the largest, most violent volcanic eruption in the history of earth. Credit: Extreme Science — Geologists estimate that 2 million years ago a cataclysmic series of volcanic eruptions in the Yellowstone Caldera was perhaps the most violent volcanic eruption in the history of earth. Credit: Extreme Science

The eruption was on such a scale that it made the 1980 Mount St. Helen’s eruption look like nothing and result in damage and destruction many miles around. Scientists estimate that the other two eruptions from the Yellowstone Super volcano came over one and two million years ago. Since the volcano is still active, there is always a possibility it will once again erupt.

However, scientists do not anticipate that there will be another eruption in the near future, at least one on such a massive scale.

Universe Today has articles on Yellowstone eruption and Yellowstone Super Volcano.

For more information, try Yellowstone Volcano and Supervolcano.

Astronomy Cast has an episode on volcanoes hot and cold.

Sources:
http://en.wikipedia.org/wiki/Yellowstone_Caldera
http://volcanoes.usgs.gov/yvo/

November 19, 2009December 24, 2015 by John Carl Villanueva

How Many Continents Are There?

[/caption]Not everyone on this planet is in agreement as with regards to the total number of continents. So how many continents are there then, according to the disagreeing parties?

Well, in Russia, Eastern Europe and Japan, the people there consider the continents of Europe and Asia as one, known as Eurasia. In other places in the world, North and South America are combined as one American continent while separating Europe and Asia instead. Thus, according to these two views, there should only be 6 continents.

There are even geographical views that prefer the presence of both a Eurasian as well as one American continent. These geographers therefore contend that there should only be 5 continents.

And if you thought that would be the lowest number, think again. There are others still who are more comfortable with a 4-continent view.

These people argue that, since Europe and Asia are actually part of one great land mass and that Asia and Africa are actually joined by an isthmus (Isthmus of Suez), as are the two Americas (being joined by the Isthmus of Panama), then there should be an Afro-Eurasian continent in addition to one American continent, Antarctica, and Australia.

But how many continents are there according to the more widely accepted view? In the most widely accepted view, there are 7 continents all in all: Asia, Africa, Europe, North America, South America, Antarctica, and Australia.

This model is preferred by the Chinese and majority of the English-speaking countries.

The final verdict as to how many continents are there might lean more on the larger numbers once the effects of global warming kick in. Once sea water levels rise, the separation between the two Americas as well as that between Africa and Asia will be more noticeable. Only the combined Europe and Asia model (a.k.a. 6-continent model) and the 7-continent model would remain.

Hundreds of millions of years from now, we really don’t know how many continents there would be. According to the continental drift theory, moving tectonic plates may rearrange the pieces of the puzzle that are the Earth’s continents.

What used to be one super continent, known as Pangaea has now been broken into 4, 5, 6, or 7 continents – depending on which side you’re more comfortable with. Therefore, its plausible, the Earth being round and all, that some of these continents will later on combine after drifting away for some time.

You can read more about plate tectonics here in Universe Today. Here are the links:

There’s more about it at USGS. Here are a couple of sources there:

Here are two episodes at Astronomy Cast that you might want to check out as well:

Sources:
Wikipedia
National Geographic

November 18, 2009December 24, 2015 by John Carl Villanueva

How Does Geothermal Energy Work

In order to understand why geothermal energy is considered an environment friendly alternative to fossil fuel, you must first be familiar with the basic workings of this technology. So how does geothermal energy work?

First of all, geothermal energy can be used in a variety of ways. There are those who utilize the heat directly for home heating (and even cooling) systems. Others use them in greenhouses, fish farms, and spas. Of course, I haven’t forgotten its most celebrated application – to produce electricity.

Thus, in answering the question, “How does geothermal energy work?”, one must first specify the specific application of the energy.

For those applications which utilize geothermal energy directly like those in fish farms, spas, and greenhouses, hot spring water is simply tapped from underneath the ground surface and redirected into these facilities.

The hot water may get its heat from magma that is able to creep upward and heat its surroundings, including the groundwater there. Magma doesn’t have to contribute heat directly though, as this melted mantle material can be found very deep underground and hence difficult to gain access to.

In some cases, where magma isn’t found in the direct vicinity, you can still obtain hot water by simply drilling deep in the ground. Always remember that the deeper you drill, the hotter the temperature gets.

Geothermal energy used to power household room heaters are extracted from the ground (not through water). During winter, ground underneath the surface is warmer than the temperature above. Heat is then extracted by using geothermal heat pumps. A typical geothermal heat pump extracts heat through a series of pipes containing either circulating water or an antifreeze solution, just like a refrigerator or an air conditioning unit.

Now for the last application mentioned earlier. How does geothermal energy work in the case of geothermal power plants?

Just like most power plants (e.g. hydro and wind power), energy is converted to electricity through the use of turbines. There are three ways of doing this.

One method directs hot steam drawn from underground into the turbine. Another draws extremely hot water from underneath, flashes it into steam, which is then directed to the turbine. The third method makes use of a heat exchanger to transfer heat from hot water drawn from underground unto a fluid (isobutane is commonly used) that is directed to the turbine.

In all three methods, the turbine is responsible for converting the kinetic energy of the directed fluid (which makes it turn) into electricity.

Universe Today has some interesting topics related to geothermal energy which you might be interested in. Here are two of them:
Geothermal Heat
Geothermal Heating

You can find more information about geothermal heat pumps from the US Department of Energy as well on the Energy Star website.

Tired eyes? Perhaps you’d like to listen to some Astronomy Cast episodes instead:
Volcanoes, Hot and Cold
Space Elevators

Sources:
http://www.ucsusa.org/clean_energy/technology_and_impacts/energy_technologies/how-geothermal-energy-works.html
http://science.howstuffworks.com/environmental/energy/geothermal-energy.htm
http://en.wikipedia.org/wiki/Geothermal_energy
http://www.eia.gov/kids/energy.cfm?page=geothermal_home-basics

November 18, 2009December 24, 2015 by John Carl Villanueva

How Do Microwaves Work

[/caption]Microwave ovens don’t operate in the same manner as conventional ovens. So how do microwaves work then? Microwave ovens take advantage of the behavior of water molecules when subjected to electromagnetic waves found in the microwave band.

To understand how this happens, we’ll have to comprehend the basic properties of water molecules and microwaves (the electromagnetic waves, not the oven).

The mickey mouse-shaped water molecule is actually a dipole. That is, one side is positively charged while the other is negative.

Microwaves used for cooking, on the other hand, are electromagnetic waves possessing frequencies around the 2.45 GHz range. Now, electromagnetic waves are waves made up of alternating electric and magnetic fields. For this discussion, we’re more concerned with the alternating electric fields because charged particles readily react when exposed to them.

That is, when a positively charged particle is exposed to an electric field, it experiences a force (due to the field) pointing in the direction of the field. By contrast, when a negatively charged particle is exposed to the same field, it experiences a force in the direction opposite to the field.

Now, since an electromagnetic wave (like the microwave) is made up of alternating electric fields, a charge exposed to it will experience forces regularly changing in direction. For water molecules, which are dipoles, the net effect would force the molecules into rotation. Again, since the fields are alternating, the rotation will change from clockwise to counterclockwise at regular time intervals.

The agitated water molecules would then possess heat energy that can rub off (much like friction) to nearby molecules. If the water molecules are well distributed in the body subjected to the microwave (like food, for example), then the entire body can heat up quickly – not to mention, uniformly.

Electromagnetic waves in the microwave range are most suitable for this purpose because the water molecules readily rotate when exposed to such frequencies.

Avoid putting in metal into the microwave oven while heating. The reason is because pointed portions of the metal can accumulate high voltages which can cause dielectric breakdown of the air inside the oven. Once this happens, some harmful gases can be produced.

Since microwave ovens normally don’t have heating elements, temperature can drop right away in the inner walls of the oven. So you’ll only need to worry about getting burned by the food and not the walls.

You can read more about electromagnetic waves here in Universe Today. Want to know about how the 25-year old mystery of X-ray emissions was solved? We’ve also written about how astronomers resolved Milky Way’s mysterious X-Ray glow

There’s more about it at NASA and Physics World. Here are a couple of sources there:
X-Ray Astronomy
X-ray Beams Thin Out

Here are two episodes at Astronomy Cast that you might want to check out as well:
X-Ray Astronomy
Optical Astronomy

Source: Wikipedia