Unusual Crater in Mars’ Mamers Valles (Gallery)

The Mars Express Spacecraft captured several images of an unusual crater in the Mamers Valles area on Mars with its High-Resolution Stereo Camera (HRSC). The crater is at the end of the long, winding valley, and contains a remarkable dark area. Scientists are not certain whether the dark colored material could have formed in-situ or if it may have been transported by the wind. Some of the structures shown here are thought to be ice-rich debris flows, and they show some resemblance to block glaciers seen on Earth.


Scientists call a region like Mamers Valles ‘fretted terrain’ because it shows numerous deep and wide labyrinth-like valleys and circular depressions which often show structures formed by flowing liquid on their even floors.

The patches of rock at the center of the depression are thought to be remnants of rock that were detached from the sides of the depression and transported to the center.

This false color image shows the differences in elevation. The image was made using elevation data obtained from an HRSC-derived high-resolution Digital Terrain Model (DTM), which is used to create elevation maps on Mars. Elevation data from the DTM has been color-coded and combined with the HRSC image so that elevation data and the image itself are displayed in a single scene.

The depression is approximately 30 km wide and 1400 m deep. It lies at the south-eastern end of Mamers Valles. The data was obtained on August 5, 2006 with a ground resolution of approximately 14 m/pixel.

The images are centered at approximately 39° north and 17° east on the planet. The valley of Mamers Valles is approximately 1000 km long, running along the boundary between the northern lowlands and southern highlands in the region of Deuteronilus Mensae.

Original News Source: ESA

Does Venus Have Rings?

Unfortunately, Venus doesn’t have rings. It also doesn’t have any moons; although, Venus might have had a moon in the past, but it probably crashed back into the planet billions of years ago.

For a planet to have rings, it must have formed further out in the Solar System, where water ice would be able to freeze into chunks of ice. It’s too warm around Venus, so that any water would be a gas or liquid. It would either collect into oceans, like Earth, or be pushed out into deeper space by the Sun’s solar wind.

Another way that planets can have rings is when micrometeoroids smash into a small moon. If the moon is really small, like Pluto’s moon Nix, material ejected from the meteoroid impact will just float off into space and form a ring around the planet. There are several moons around Saturn which create rings in this way, and scientists think that Pluto’s moons might form rings in the same way.

Sorry, no rings for Venus.

Does Pluto Have Rings?

Saturn has rings and Jupiter has rings. Does Pluto have rings? Astronomers have no idea. Pluto is so far away that it’s impossible to get a clear view of Pluto from here on Earth.

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But scientists think that it’s possible that Pluto does have rings. This idea comes from the fact that Pluto has two tiny moons, Nix and Hydra. They’re just a few km across, and have very little gravity. So any micrometeoroid impacts on these moons will kick up material into orbit around Pluto.

Instead of falling back down onto the moons, this impact material would drift into rings around Pluto. Astronomers think it could actually survive for up to 100,000 years. This is a similar process that creates some of the rings around Saturn and Jupiter.

If this is true, it would constitute the first set of rings around a solid object (in this case a dwarf planet), rather than a gas giant planet.

When NASA’s New Horizons mission arrives at Pluto in 2015, it might be able to detect these faint rings, and confirm the theory.

How Far is Pluto from Earth?

The planet Earth has a slightly eccentric orbit. This means that its distance from the Sun can vary slightly as the Earth travels an elliptical path around the Sun. Pluto has an extremely elliptical orbit, varying its distance dramatically from the Sun dramatically.

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So the closest distance between the Earth and Pluto occurs when Earth is at its most distant from the Sun, and Pluto is at its closest. And the Sun, Earth and Pluto are lined up in a perfect line. When this happens, Pluto and Earth would be separated by 4.2 billion km.

At their most distant, Earth would be at its furthest at the opposite side of the Sun from Pluto. At this point, Earth and Pluto would be separated by 7.5 billion km.

And so, the distance from Earth to Pluto ranges between these two distances.

Weekend SkyWatcher’s Forecast – May 16-18, 2008

Sinus Iridum by Wes Higgins

“Everybody dancing in the moonlight… Dancing in the moonlight… Everybody feeling warm and bright… It’s such a fine and natural sight… Everybody dancing in the moonlight.” Oh! Greetings, fellow SkyWatchers! Pardon me while I celebrate the return of Spring and enjoy viewing the Moon. This weekend will be a terrific time for you to dance, too. Talk a waltz around the “Bay of Rainbows” as you view Sinus Iridum and enjoy the cool blues with Spica. You’ll be seeing double before the weekend is out. Time to dust off the optics and turn and eye to the sky, because… Here’s what’s up!

Friday, May 16, 2008 – Tonight would be a wonderful opportunity for Moongazers to return to the surface and have a look at the peaceful Sinus Iridum area. If you’ve been clouded out before, be sure to have a look for the telescopic Lunar Club challenges Promontoriums Heraclides and LaPlace. What other craters can you discover in the area?

Palomar Observatory, courtesy of Caltech
If you’re up for a bit more of a challenge, then let’s head about 59 light-years away for star 70, in Virgo. You’ll find it located about six degrees northeast of Eta (RA 13 28 25 Dec +13 46 43) and right in the corner of the Coma-Boötes-Virgo border. So what’s so special about this G-type, very normal-looking, 5th magnitude star?

It’s a star that has a planet.

Long believed to be a spectroscopic binary because of its 117 day shift in color, closer inspection has revealed that 70 Virginis actually has a companion planet. Roughly seven times larger than Jupiter and orbiting no further away than Mercury from its cooler-than-Sol parent star, 70 Virginis B just might well be a planet cool enough to support water in its liquid form. How “cool” is that? Try about 85 degrees Celsius…

Saturday, May 17, 2008 – Today in 1835, J. Norman Lockyer was born. While that name might not stand out, Lockyer was the first to note previously unknown absorption lines while making visual spectroscopic studies of the Sun in 1868. Little did he know at the time, he had correctly identified the second most abundant element in our universe – helium – an element not discovered on Earth until 1891! Also known as the “Father of Archeoastronomy,” Sir Lockyer was one of the first to make the astronomical connection with ancient structures such as Stonehenge and the Egyptian pyramids. (As a curious note, 14 years after Lockyer’s notation of helium, a Sun-grazing comet made its appearance in photographs of the solar corona taken during a total eclipse in 1882… It hasn’t been seen since.)

Spica by John ChumackIf you would like to see a helium-rich star, look no further tonight than Alpha Virginis – Spica. You can’t miss it because it’s so near the Moon! As the sixteenth brightest star in the sky, this brilliant blue-white “youngster” appears to be about 275 light-years away and is about 2300 times brighter than our own Sun. Although we cannot see it visually, Spica is a double star. Its spectroscopic companion is roughly half its size and is also rich in helium.

Crater Copernicus by Wes HigginsSunday, May 18, 2008 – On this day in 1910, Comet Halley transited the Sun, but could not be detected visually. Since the beginning of astronomical observation, transits, eclipses and occultations have provided science with some very accurate determinations of size. Since Halley could not be spotted against the solar surface, we knew almost a century ago that the nucleus had to be smaller than about 100 kilometers. To get a rough idea of this size, take a look at crater Copernicus about midway along the western hemisphere of the Moon. What’s its diameter? Oh, about the same size as a certain comet!

Now let’s have a look at a very bright and changeable lunar feature which is often overlooked. Starting with the great grey oval of Grimaldi, let your eyes slide along the terminator toward the south until you encounter the bright crater Byrgius. Named for Joost Bürgi, who made a sextant for Tycho Brahe, this “seen on the curve” crater is really quite large with a diameter of 87 kilometers. Perhaps its most interesting feature is the high-albedo Byrgius A, which sits along its eastern wall line and produces a wonderfully bright ray system. While it’s noted as a Lunar Club II challenge, it’s also a great crater to help add to your knowledge of selenography!

It’s time to add to our double star list as we hunt down Zeta Boötes located about seven degrees southeast of Arcturus (RA 14 41 08 Dec +13 43 42). This is a delightful multiple star system for even small telescopes – but not an easy one. The Zeta pairing has an extremely elliptical orbit: the distance between the stars varies from as little as the Earth-Sun distance to as much as 1.5 times the radius of Pluto’s orbit!

Another great target for a bright night is Delta Corvi (RA 12 29 51 Dec -16 30 55). 125 light-years away, it displays a yellowish-colored primary and a slightly blue secondary that’s an easily split pair in any telescope, and a nice visual double with Eta in binoculars. Use low power and see if you can frame this bright grouping of stars in the same eyepiece field.

Wising you good luck, clear skies and a wonderful weekend! 😉

This week’s awesome photos are of Sinus Iridum and Copernicus by the one and only Wes Higgins, 70 Virginis – Credit: Palomar Observatory, courtesy of Caltech and Alpha Virginis: Spica, by none other than the incredibly talented John Chumack. Spectacular!

Surface of Venus

The "impact farm:, an area on Venus marked by impact craters and volcanic activity. Credit: NASA/JPL

The surface of Venus is a hellish place, with vast regions shaped by volcanic activity. In fact, Venus has many more volcanoes than Earth. It has more than 150 regions across the planet shaped by volcanoes.

And from this, you would think that Venus is more volcanic than Earth, but actually, it’s just that the regions of volcanic activity weren’t covered up as they have been here on Earth. The surface of Earth is constantly reshaped by tectonic activity, where plates on the crust of the planet float atop a layer of magma. These plates can slide underneath one another, and any features on the surface are destroyed.

For some reason, plate tectonics on Venus stopped billions of years ago. Planetary scientists think that the high temperatures on Venus shut down the cycle of plate tectonics. Volcanic features created on the planet billions of years ago are still visible, while they would have been obscured long ago on Earth.

Scientists think there is still active volcanism on Venus.

There are more than 1,000 impact craters on Venus, distributed across the planet. While craters are eroded here on Earth, they’re still in pristine condition on Venus. The craters range in size from 3 km to 280 km in diameter.

Retrograde Rotation of Venus

Could Jupiter throw the planets into eachother? (NASA)

Of all the planets in the Solar System, Venus has a unique rotation. Seen from above, all of the planets rotate in a counter-clockwise direction. And this is what you would expect if all the planets formed from the same planetary nebular billions of years ago.

And yet, the rotation of Venus is clockwise, what astronomers call “retrograde”. Venus rotates backwards. Of course, since the length of a day on Venus is longer than a year, this rotation happens very slowly.

Why does Venus rotate backwards? One possibility is that Venus rotated normally when it first formed from the solar nebula, and then the tidal effects from its dense atmosphere might have slowed its rotation down.

Another theory is that a series of gigantic impacts early on in Venus’ history might have stopped or even reversed its rotation altogether. A similar impact happened to Earth billions of years ago, which formed the Moon.

The Diameter of Venus

The diameter of Venus is 12,100 km. That is 95% of the diameter of Earth. There are many similarities between the two planets, but there are many more extreme differences.

Venus and Earth are two of the four terrestrial planets in our Solar System. Mercury and Mars are the other two. Venus has a surface gravity that is 8.87 m/s2 or 90% of the gravity here on Earth. The planet has 86% of the volume that Earth has along with 82% of the mass. The planet’s density is nearly identical at 5.243 g/cm3. The similarities end there.

The average surface temperature of Venus is about 9 times higher than it is on Earth. It is 462°C there and the hottest deserts on Earth rarely see 50°C. The atmospheric pressure at surface level is 92 times greater than it is here, while the atmosphere itself contains 96% carbon dioxide. If a human managed to survive the pressure and could find a supply of oxygen, there is the sulfuric acid droplets and clouds along with heavy amounts of volcanic ash that are floating in the ”air”.

Like Earth, Venus has a magnetic field that protects it from the solar wind. Unlike Earth, its magnetic field is not created by a dynamo effect. In order for a planet to create its own magnetic field in this way, it has to have a liquid core that is spinning and the ability to release heat through convection. Venus is not capable of convection because the surface was nearly covered in lava between 300 and 500 million years ago. When that lava hardened it prevented the possibility of tectonic action and heat convection. The Venusian magnetic field is created by an interaction of the solar wind and the ionosphere of the planet. This reaction creates a weaker field than the one on Earth, so the planet is susceptible to cosmic radiation.

The entire diameter of Venus is covered in volcanoes and the remnants of volcanoes. There are 1,000 of them that are over 20 km in diameter scattered among thousands of smaller ones. There are some large impact craters, but no small ones. Any small meteorites would burn up in the thick atmosphere.

That is a lot of information to throw at you. Again, the diameter of Venus is 12,100 km and is very close to that of Earth. Hopefully, you found all of the information that you need and good luck with any further research you need to do.

We have written many articles about Venus for Universe Today. Here’s an article about the atmosphere of Venus, and here’s an article about how far Venus is from the Sun.

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 all about Venus. Listen here, Episode 50: Venus.

Reference:
NASA

Carnival of Space #54

The Mice Galaxies (NGC 4676) are famous interacting galaxies currently undergoing a process of collision and merger. The long tail on the right side is a result of the gravitational tidal forces during the merging process. When galaxies merge, a significant amount of molecular gas flows into the central region, promoting the formation of numerous stars and facilitating the growth of supermassive black holes. Image Credit: NASA, H. Ford (JHU), G. Illingworth (UCSC/LO), M.Clampin (STScI), G. Hartig (STScI), the ACS Science Team, and ESA.
The Mice Galaxies (NGC 4676) are famous interacting galaxies currently undergoing a process of collision and merger. The long tail on the right side is a result of the gravitational tidal forces during the merging process. When galaxies merge, a significant amount of molecular gas flows into the central region, promoting the formation of numerous stars and facilitating the growth of supermassive black holes. Image Credit: NASA, H. Ford (JHU), G. Illingworth (UCSC/LO), M.Clampin (STScI), G. Hartig (STScI), the ACS Science Team, and ESA.

We have another new host for the Carnival of Space. This week we look to David S. F. Portree and his blog Altair VI.

Click here to read the Carnival of Space #54

And if you’re interested in looking back, here’s an archive to all the past carnivals of space. If you’ve got a space-related blog, you should really join the carnival. Just email an entry to [email protected], and the next host will link to it. It will help get awareness out there about your writing, help you meet others in the space community – and community is what blogging is all about. And if you really want to help out, let me know if you can be a host, and I’ll schedule you into the calendar.

Finally, if you run a space-related blog, please post a link to the Carnival of Space. Help us get the word out.