Is the Earth Round?

The Earth isn’t flat, that’s for sure. And if you look at a photograph, the Earth really looks round. But how round is it?

The actual shape of the Earth is actually an oblate spheroid – a sphere with a bulge around the equator. The Earth is bulged at its equator because it’s rapidly rotating on its axis. The centripetal force of the rotation causes the regions at the equator to bulge outward. And it actually makes a pretty big difference. The diameter of the Earth, measured across the equator is 43 km more than when you measure the diameter of the Earth from pole to pole.

This bulge has some interesting implications. For example, it means that the point on Earth furthest from the center isn’t actually Mount Everest, but Mount Chimborazo in Ecuador. Only because Chimborazo is closer to the Earth’s equator.

So how smooth is the Earth. When billiard balls are manufactured, they aim for a tolerance of 0.22%. The Earth has a tolerance of 0.17%, so it’s actually smoother than a billiard ball. If you could hold the Earth in your hands, it would feel smoother than a billiard ball.

But the Earth definitely isn’t flat.

We have written many articles about the Earth for Universe Today. Here’s a cool article about looking at the Earth as if it’s an extrasolar planet.

Want more resources on the Earth? Here’s a link to NASA’s Human Spaceflight page, and here’s NASA’s Visible Earth.

We have also recorded an episode of Astronomy Cast about Earth, as part of our tour through the Solar System – Episode 51: Earth.

What is the Tallest Volcano on Earth?

Mauna Kea. Image credit: USGS

[/caption]
The tallest volcano on Earth is Mauna Kea, one of the 5 volcanos that make up the Big Island of Hawaii. The summit of Mauna Kea is 4,205 meters above sea level, but its true height is much larger. When measured from the sea floor, Mauna kea is more than 9,000 meters tall, making it the tallest mountain on Earth.

Mauna Kea is part of the network of volcanos above the Hawaiian hotspot. The tectonic plate that has the Hawaiian islands is slowly moving above the hotspot, and it recently carried Mauna Kea away from the hotspot. Scientists believe that Mauna Kea is now dormant; it last erupted about 4,500 years ago. Although, researchers do think it’s going to erupt again, the time between eruptions is measured in hundreds of years. The most active volcano on the island, Kilauea, erupts every few years.

Even though the Hawaiian islands are warm and tropical, Mauna Kea is so tall that it has regular snowfalls in the winter months. Geologists have even found deposits created by glaciers during recent ice ages. There were probably three glacial episodes in the last 200,000 years. People regularly ski on the slopes of Mauna Kea.

Although Mauna Kea is the tallest volcano, it’s only about 40 meters taller than the nearby Mauna Loa, which is the biggest volcano on Earth. Mauna Loa has more than 75,000 cubic kilometers of material.

And the biggest volcano in the Solar System isn’t on Earth, but on Mars. The enormous Olympus Mons is 27 km tall, and contains 100 times more material than Mauna Loa.

We have written many articles about the Earth for Universe Today. Here’s an article about the biggest volcano on Earth, and here’s an article about the biggest volcano in the Solar System.

Want more resources on the Earth? Here’s a link to NASA’s Human Spaceflight page, and here’s NASA’s Visible Earth.

We have also recorded an episode of Astronomy Cast about Earth, as part of our tour through the Solar System – Episode 51: Earth.

What is the Biggest Volcano on Earth?

Mauna Loa. Image credit: USGS

[/caption]
The largest volcano on Earth is Mauna Loa, which is one of the 5 volcanoes that make up the Big Island of Hawaii. When we talk about biggest volcano here, we’re talking about the volcano that has the biggest volume, and that’s Mauna Loa. It’s made up of an estimated 75,000 cubic kilometers of material.

Mauna Loa is an active shield volcano, and scientists think that it has been erupting for about 700,000 years; it emerged through the surface of the ocean about 400,000 years ago. The active magma for Mauna Loa comes from the Hawaiian hotspot. But the plate carrying the massive volcano is slowly carrying it away from the hotspot, and it will go extinct in the next 500,000 to 1 million years. It last erupted in 1984, and destroyed homes and villages in 1926 and 1950.

The volcano measures 4,169 meters above sea level, but that’s not its true height. Measured from the sea floor, Mauna Loa is really taller than 9,000 meters – that’s taller than Mount Everest. But Mauna Loa isn’t the tallest volcano, that’s actually its neighbor, Mauna Kea, which is about 40 meters taller.

The biggest volcano in the Solar System isn’t on Earth, but on Mars. Olympus Mons, on Mars, measures 27 km high, and has about 100 times the volume of Mauna Loa.

We have written many articles about the Earth for Universe Today. Here’s an article about the biggest volcano in the Solar System, and here are some great images of a lightning storm around a volcano.

Want more resources on the Earth? Here’s a link to NASA’s Human Spaceflight page, and here’s NASA’s Visible Earth.

We have also recorded an episode of Astronomy Cast about Earth, as part of our tour through the Solar System – Episode 51: Earth.

Next ATV Will Be Named Johannes Kepler

Jules Verne arrives at the ISS. Johannes Kepler is next... (NASA)

[/caption]

The next Automated Transfer Vehicle (A T V) to be launched to supply the International Space Station (ISS) has been officially named. Currently being assembled in Germany, the next ATV will honour the great 17th Century German scientist, Johannes Kepler.

The very first ATV was named after the legendary French science fiction writer, Jules Verne, and launched on an extended 5 month mission to the orbiting outpost where it delivered supplies, gave the station a helpful re-boost and then carried out an extreme garbage disposal effort, burning up over the Pacific Ocean on September 5th, 2008.

After it is launched on a similar resupply mission in 2010, the same fate awaits ATV Johannes Kepler. Or does it

The ATV is Europe’s most advanced spacecraft ever built. Last year, Jules Verne wowed the world as it was launched into orbit, completed a flyby of the station (at a distance of 30 km) and then carried out a series of tests (including the critical Collision Avoidance Manoeuvre) before waiting in a parking orbit, 2000 km from its destination.

This was a particularly busy time for the ISS as Jules Verne had to wait for Space Shuttle Endeavour to finish its mission (STS-123) to attach the Japanese Kibo module and Canadian robotic arm. After Endeavour returned to Earth, the ATV was clear to dock on April 3rd.

So next year, it will be ATV Johannes Kepler’s turn to carry out a fully automated docking procedure with the space station to deliver food, water, propellant and oxygen. As with Jules Verne, Johannes Kepler is expected to provide a re-boost option, pushing the ISS to a slightly higher orbit.

However, Johannes Kepler might be saved from the fiery re-entry its predecessor had to endure. The European Space Agency, overjoyed at the success of Jules Verne, has asked the space industry for advice on how the ATV might be upgraded, to allow for the safe return of cargo to Earth and possible astronaut transportation. A feasibility study was approved at a meeting in The Hague in November 2008.

Interestingly, there will be another mission already in space in 2010 bearing the same name as the second ATV. The exoplanet-hunting Kepler telescope is set for launch next month.

Source: BBC

New HiRISE Images: Winter Turning to Spring in Mars’ Southern Hemisphere

Proctor Crater on Mars during winter. Credit: NASA/JPL/U of AZ

[/caption]
If you’ve never seen the “Springtime on Mars 2020” video, its a fun (if not Wall-E-ish) view of what Mars could be like sometime in the future. But now in 2009, winter is turning to spring in Mars’ southern hemisphere, and the HiRISE camera on board the Mars Reconnaissance Orbiter is busy snapping high resolution images of planet’s surface. In the winter the dunes shown here in Proctor Crater are covered with seasonal carbon dioxide frost (dry ice). In the spring, the frost gradually evaporates but lingers in protected regions. In this color image bright ice deposits in sheltered areas highlight the ripples on the dunes. Now that MRO has been in orbit for two Martian winters, this image of Proctor Crater can be compared with the images of these dunes that were taken during the first year of MRO’s mission. Scientists are comparing the images to study inter-annual variability. See an image from January 2007 of Proctor Crater below, as well as more new images from HiRISE.

Proctor Crater dune field, 2007. Credit: NASA/JPL/U of AZ
Proctor Crater dune field, 2007. Credit: NASA/JPL/U of AZ

Here’s how Proctor Crater looked two years ago (one Martian late winter ago), in January 2007. The crater is located -47.2 degrees latitude, and 33.9 degrees longitude East.
South pole CO2.  Credit: NASA/JPL/U of AZ
South pole CO2. Credit: NASA/JPL/U of AZ

Every southern winter the south polar region of Mars is covered with an approximately 1 meter deep layer of frozen carbon dioxide (dry ice). In the spring, when the sun begins to warm the surface below the translucent ice, gas flow under the ice carries loose dust from the surface up onto the top.

The dust falls to the surface in fans, whose orientation is determined by the direction of the local wind flow. Fans from one source region pointing in multiple directions show how the wind direction has changed. Narrow fans pointing in just one direction are the most recent. Alternatively, the vent from the surface may have re-annealed, such that these fans were formed over a very limited time span.

Hellas Basin.  Credit: NASA/JPL/U of AZ
Hellas Basin. Credit: NASA/JPL/U of AZ

Not quite so far south, at just -28.4 degrees latitude, is Hellas Basin. The detail of this image is amazing, and even though its not a 3-D image, it almost appears so, because of the depth of the detail.

This image shows part of the floor of an impact crater on the northern rim of the giant Hellas Basin.

Hellas includes the lowest elevations on Mars, and may have once held lakes or seas; layered rock outcrops occur around much of the edge of the basin. At this site, a large impact crater (about 90 kilometers across) was partly filled by layered rocks. These rocks on the crater floor are now eroding and forming strange pits.

Here, the layers are mostly exposed on a steep slope which cuts across much of the image. On this slope, they crop out as rocky stripes, some continuous and others not. The material between the stripes is mostly covered by debris, but some areas of exposed rock are visible. The slope is capped by a thick, continuous layer that armors it against erosion; once this cap is gone, the lower material is removed rapidly, forming the steep slope. At the base of this slope, rocks on the floor of the pit appear bright and heavily fragmented by cracks known as joints.

Great images — keep ’em coming, HiRISE!

For more info see the HiRISE site.

Where In The Universe #43

It’s Wednesday, so that means its time for another “Where In The Universe” challenge to test your visual knowledge of the cosmos. See if you can name where in the Universe this image is from, and give yourself extra points if you can name the spacecraft responsible for the image. Make your guess and post a comment. Check back sometime on Thursday to find the answer and see how you did (and yes, I’ll try to remember to post the answer in a timely fashion this week!)

UPDATE: The answer has now been posted below.

Pretty much everyone said this was Europa, and guess what, you’re right! This highly detailed image of Jupiter’s moon Europa was taken by the Galileo spacecraft. It’s a processed image to show the differences in materials that cover the ice. The red linear features are cracks and ridges that stretch for thousands of kilometres across the moon’s surface, resulting from tides raised by the pull of Jupiter. The mottled red terrain shows areas that have been disrupted and where ice blocks have moved around. The red material is thought to be a non-ice contaminant, such as salts brought up from the ocean thought to lie beneath Europa’s icy shell. Image: NASA/JPL/University of Arizona.

Great job everyone, and check back again next week for another WITU Challenge!

What is the Biggest Island on Earth?

Greenland. Image credit: NASA
Greenland. Image credit: NASA

The largest island on Earth is Greenland, with a total land area of 2.2 million km2.

This is a bit of a complicated question because it’s hard to define the difference between an island and a continent. Both Antarctica and Australia are larger than Greenland, but they’re continents, so they’re out.

As you probably know, Greenland sits up near the Earth’s north pole, in between North America and Europe. More than 80% of the island is covered by glaciers, some of which can be more than a kilometer thick. With such an extreme environment, Greenland is sparsely populated; roughly 60,000 people live on the island, and most of those live in the capital city of Nuuk, on the southern island.

If you’re interested, the second largest island on Earth is New Guinea, with 785,000 square kilometers. And the third largest island is Borneo, with 748,000 km.

We have written many articles about the Earth for Universe Today. Here’s an article about how scientists measure melting ice in Greenland, and how snow melt is on the rise in Greenland.

Want more resources on the Earth? Here’s a link to NASA’s Human Spaceflight page, and here’s NASA’s Visible Earth.

We have also recorded an episode of Astronomy Cast about Earth, as part of our tour through the Solar System – Episode 51: Earth.

Albedo of the Earth

The albedo of the Earth is 0.367.

That’s the simple answer, now here’s the more complex one. Astronomers use the term “albedo” to define the amount of light that an object in the Solar System reflects. For example, if a planet was perfectly shiny, it would have an albedo of 1.00; it would reflect 100% of the light that hit it. If a planet was perfectly dark, it would have an albedo of 0, and so it would reflect 0% of the light that struck it.

The object with the highest albedo in the Solar System is Saturn’s moon Enceladus, with an albedo of 99%. On the other hand, asteroids can have albedos as low as 4%. The Earth’s moon has an albedo of about 7%. Can you imagine if we had Enceladus for a moon? Now that would be bright.

The albedo of the Earth is very important because it helps define the temperature of the planet. Fresh snow has an albedo of 90%, while the ocean has a very low albedo; land areas range from 0.1 to 0.4.

NASA’s Terra and Aqua satellites are constantly measuring the albedo of the Earth with their MODIS instruments, to help detect any evidence that the albedo is changing over time.

We have written many articles about the Earth for Universe Today. Here’s an article about how scientists track Earthshine on the Moon. And here’s a more detailed article about the albedo of the Moon.

Want more resources on the Earth? Here’s a link to NASA’s Human Spaceflight page, and here’s NASA’s Visible Earth.

We have also recorded an episode of Astronomy Cast about Earth, as part of our tour through the Solar System – Episode 51: Earth.

Next Big Planetary Mission: To Jupiter and Its Moons

Artist concept of proposed missions to the Jupiter system (left) and the Saturn system (right). Image credit: NASA/JPL

[/caption]
At a meeting last week between NASA and ESA, the two space agencies narrowed down the choices for the next big flagship planetary missons, which will be joint efforts between the US and Europe. A mission to Jupiter and its four largest moons will be the primary mission the two space agencies will focus on, while they continue to plan for another potential mission to visit Saturn’s largest moon Titan and Enceladus. The two missions, the Jupiter System Mission and the Titan Saturn System Mission, are the result of NASA and ESA merging their separate mission concepts.

“This joint endeavour is a wonderful new exploration challenge and will be a landmark of 21st Century planetary science,” said David Southwood, ESA Director of Science and Robotic Exploration. “What I am especially sure of is that the cooperation across the Atlantic that we have had so far and we see in the future, between America and Europe, NASA and ESA, and in our respective science communities is absolutely right. Let’s get to work.”

The Europa Jupiter System Mission would use two robotic orbiters to conduct detailed studies of the giant gaseous planet Jupiter and its moons Io, Europa, Ganymede and Callisto. NASA would build one orbiter, initially named Jupiter Europa. ESA would build the other orbiter, initially named Jupiter Ganymede. The probes would launch in 2020 on two separate launch vehicles from different launch sites. The orbiters would reach the Jupiter system in 2026 and spend at least three years conducting research.

Europa.  Credit: NASA
Europa. Credit: NASA

Europa has a surface of ice, and scientists theorize it has an ocean of water beneath that could provide a home for living things. Ganymede, the largest moon in the solar system, is the only moon known to have its own internally generated magnetic field and is suspected to have a deep undersurface water ocean. Scientists long have sought to understand the causes of the magnetic field. Callisto’s surface is extremely heavily cratered and ancient, providing a clear indication of a record of events from the early history of the Solar System. Finally, Io is the most volcanically active body in the solar system.

“The decision means a win, win situation for all parties involved,” said Ed Weiler, associate administrator for NASA’s Science Mission Directorate in Washington. “Although the Jupiter system mission has been chosen to proceed to an earlier flight opportunity, a Saturn system mission clearly remains a high priority for the science community.”

The future Titan Saturn System Mission would consist of a NASA orbiter and an ESA lander and research balloon.

Both of these proposed missions will set the stage for future planetary science research. These outer planet flagship missions could eventually answer questions about how our solar system formed and whether life exists elsewhere in the universe.

Source: JPL

New Recipe for Dwarf Galaxies: Start with Leftover Gas

NASA's Galaxy Evolution Explorer reveals, for the first time, dwarf galaxies forming out of nothing more than pristine gas likely leftover from the early universe. Credit: NASA/JPL-Caltech/DSS

[/caption]

Apparently, dwarf galaxies can spring out of thin air.

Astronomers using NASA’s Galaxy Evolution Explorer have spotted unexpected new galaxies in the constellation Leo that appear to be forming out of nothing more than pristine gas, probably leftover from the early universe.  The gas lacks both dark matter and metals — previously thought to be building blocks for galaxy formation.

Dwarf galaxies are relatively small collections of stars that often orbit around larger galaxies like our Milky Way. Though never seen before, the researchers say this new type of dwarf galaxy may be common throughout the more distant and early universe, when pristine gas was more pervasive. Their discovery appears in this week’s issue of the journal Nature.

The newly described dwarf galaxies are in the Leo Ring, a huge cloud of hydrogen and helium that traces a ragged path around two massive galaxies in the constellation Leo. The cloud is thought likely to be a primordial object, an ancient remnant of material that has remained relatively unchanged since the very earliest days of the universe. Identified about 25 years ago by radio waves, the ring cannot be seen in visible light.

“This intriguing object has been studied for decades with world-class telescopes operating at radio and optical wavelengths,” said lead study author David Thilker of Johns Hopkins University in Baltimore. He added that no stars were ever seen in the gaseous regions before. 

“But when we looked at the ring with the Galaxy Evolution Explorer, which is remarkably sensitive to ultraviolet light, we saw telltale evidence of recent massive star formation. It was really unexpected. We are witnessing galaxies forming out of a cloud of primordial gas.”

Our local universe contains two large galaxies, the Milky Way and the Andromeda galaxy, each with hundreds of billions of stars, and the Triangulum galaxy, with several tens of billions of stars. It also holds more than 40 much smaller dwarf galaxies, which have only a few billion stars. Invisible dark matter, detected by its gravitational influence, is a major component of both giant and dwarf galaxies with one exception — tidal dwarf galaxies.

Tidal dwarf galaxies condense out of gas recycled from other galaxies and have been separated from most of the dark matter with which they were originally associated. They are produced when galaxies collide and their gravitational masses interact. In the violence of the encounter, streamers of galactic material are pulled out away from the parent galaxies and the halos of dark matter that surround them.

Because they lack dark matter, the new galaxies observed in the Leo Ring resemble tidal dwarf galaxies, but they differ in a fundamental way. The gaseous material making up tidal dwarfs has already been cycled through a galaxy. It has been enriched with metals — elements heavier than helium — produced as stars evolve. “Leo Ring dwarfs are made of much more pristine material without metals,” Thilker said. “This discovery allows us to study the star formation process in gas that has not yet been enriched.”

Large, pristine clouds similar to the Leo Ring may have been more common throughout the early universe, Thilker said, and consequently may have produced many dwarf galaxies yet to be discovered that also lack dark matter.

Source: Caltech

leo_dwarf_galaxies
The forming dwarf galaxies shine in the far ultraviolet spectrum, rendered as blue in the call-out on the right hand side of this image. Near ultraviolet light, also obtained by the Galaxy Evolution Explorer, is displayed in green, and visible light from the blue part of the spectrum here is represented by red. The clumps (in circles) are distinctively blue, indicating they are primarily detected in far ultraviolet light. The faint blue overlay traces the outline of the Leo Ring, a huge cloud of hydrogen and helium that orbits around two massive galaxies in the constellation Leo (left panel). Credit: NASA/JPL-Caltech/DSS