Author: Fraser Cain

When astronomers looked at the orbits of the planets, they felt that there could be a planet “missing” in between the orbits of Jupiter and Mars. In fact, this is where the asteroid belt is; a collection of large and small rocky objects.

Could this be the missing planet? Astronomers think that Jupiter formed early enough that its gravity ruined the chances for another planet to assemble itself in the region between Mars and Jupiter.

When you add up the total mass of all the objects in the asteroid belt, you only get enough material to be about the same size as Saturn’s relatively small moon Rhea. So you couldn’t really call that a planet.

However, back in the day when Jupiter formed, it’s possible that there was much more material in this region than what we see today. The intense gravity of Jupiter would have reached out and perturbed the orbits of the planetesimals in the region. Some would have been kicked out into the outer Solar System, and others would have been driven inward to collide with the Sun, or crash into the inner planets.

It’s also possible that a planet was there in the early Solar System, but then a large collision knocked it off course, and it spiraled inward or outward, never to be seen from again.

Here’s an article from Universe Today about water on asteroid Ceres, and an asteroid that broke up more than 8 million years ago.

Here’s the question answered at Astronomy Cafe, and a Wikipedia article about Phaeton (a hypothetical planet between Mars and Jupiter).

Finally, if you’d like to learn more about planet Mars in general, we have done several podcast episodes about the Red Planet at Astronomy Cast. Episode 52: Mars, and Episode 91: The Search for Water on Mars.

The planet Mars is one of the most photographed objects in the Solar System. There are hundreds of thousands of images of Mars, seen from the ground, from orbit around the planet, and from here on Earth. With so many photos of Mars to choose from, it’s impossible to show them all, but we can show some of our favorites.

---

This is a picture of Mars captured by the Hubble Space Telescope on October 28, 2005, when Mars was just about to make its closest approach to Earth. If you look carefully, you can see a regional dust storm. When this amazing pic was taken, the dust storm was about the size of Texas.

---

This is a picture of Mars captured by NASA’s Mars Exploration Opportunity rover. It shows the Victoria Crater on the surface of Mars. Opportunity slowly made its way up to the edge of the crater, and then crawled down inside to examine the rock walls for past evidence of liquid water on the surface of Mars.

---

This looks like a plain old image of a crater on Mars, but it’s much more special than that. The inset box on the left-hand side is NASA’s Phoenix Mars Lander descending to the surface of Mars. The image was captured by NASA’s Mars Reconnaissance Orbiter which had been positioned to watch the spacecraft descend.

---

The largest canyon in the Solar System is the amazing Valles Marineris on Mars. Stretching more than 4,000 km long, and as deep as 7 km, it would cross the United States if put on Earth. This is a photograph of just one portion of the canyon, captured by ESA’s Mars Express spacecraft.

---

More than 1000 separate pictures of Mars captured by the Viking Orbiter were stitched together to create this composite image of Mars. This is one of the most beautiful, high-resolution images of Mars ever captured. Olympus Mons and the other large volcanoes are on the left-hand side of the photo. Valles Marineris is down at the bottom, and the northern polar ice cap is up at the top.

Want more photographs of Mars, just click here to search Universe Today and see hundreds of photographs.

Here’s NASA’s photo gallery of Mars. And additional pictures of Mars from Nine Planets.

Finally, if you’d like to learn more about planet Mars in general, we have done several podcast episodes about the Red Planet at Astronomy Cast. Episode 52: Mars, and Episode 91: The Search for Water on Mars.

In June of 1976, NASA’s Viking 1 mission began sending back images from the Martian surface. A few of those images contained what is now known as ”the face on Mars”. These images are from an area known as the Cydonia Mensae. The original images were dismissed, but were reconsidered when a second set of images from a different angle showed the same face.

The Cydonia area of the northern hemisphere of Mars includes: Cydonia Mensae, which is an area of flat-topped mesa-like features, Cydonia Colles, which is an area of hills, and Cydonia Labyrinthus, a group of intersecting valleys. The face is located among a few craters in the area, specifically about half-way between Arandus Crater and Bamberg Crater. This is an area where the heavily bombarded southern hemisphere begins to transition into the smooth, relatively uncratered north.

The meas seems appears to be a face because of an optical illusion called pareidolia. Pareidolia is a psychological phenomenon where a vague and random image is perceived as significant. Common examples include seeing animals or faces in clouds or the Virgin Mary in a pancake. The mesa has a few higher areas where you would expect to see human features and the mind fills in the blanks.

Of course, UFO buffs(read fools here, please) jumped on the images as evidence that there was a past culture on the planet. Some even went so far as to believe that the Martians formed the face to communicate with a less developed human race. Unfortunately, it took many years to develop the technology to image the mesa more clearly, so these crackpots had plenty of time to spread their poisoned opinions.

More recent images from the Mars Global Surveyor and other spacecraft have shown that the face on Mars is nothing other than a hill. The shadows that seem to be the facial features nearly disappear in high resolution imagery. Click here for comparison photos.

All conspiracy theories aside, the face on Mars had many scientists intrigued for a while, trying to determine what had created the illusion. Thankfully, new technology has nearly eradicated the diseased thinking spread by UFO junkies.

Here’s an article about a recent image of the face on Mars.

Enjoy a NASA article about the face on Mars, and information on the Mars face from the MSSS team.

Finally, if you’d like to learn more about Mars in general, we have done several podcast episodes about the Red Planet at Astronomy Cast. Episode 52: Mars, and Episode 91: The Search for Water on Mars.

Sources:
NASA Image Gallery
NASA Science

If you were stuck inside your house, you’d never know what it looks like from the outside. That’s the situation with the Milky Way. We’re inside it, so we don’t really know what its structure looks like. There are other examples of grand spirals that we can see, but this is like seeing other houses outside your window; you just can’t be sure. Astronomers have developed a detailed map of the Milky Way, and realized that they were giving our home galaxy too many arms; it’s only got 2, and not 4 like astronomers originally thought.

The new revelation was made possible thanks to NASA’s Spitzer Space Telescope, which sees in the infrared spectrum, and can peer though the gas and dust that obscures the plane of the Milky Way.

Previous maps of the Milky Way were first developed in the 1950s, when astronomers used radio telescopes to trace out the spiral arms of our home galaxy. They focused on gas clouds, and revealed what they thought were 4 major star-forming arms: Norma, Scutum-Centaurus, Sagittarius and Perseus.

We live in minor arm called the Orion Arm, or the Orion Spur, located between the Sagittarius and Perseus Arms.

And then in 2005, astronomers used infrared telescopes to pierce through the clouds of gas and dust to see that the central bar in the middle of the Milky Way extends much further than previously believed.

In a new survey by Spitzer, astronomers merged together 800,000 photographs containing over 110 million stars. Software counted up the number of stars and measured their density.

As expected, astronomers found an increase in density in stars towards the Scutum-Centaurus Arm, but no increase towards the Sagittarius and Norma arms. The Perseus arm wraps around the outer portion of our galaxy and can’t be seen in the Spitzer images.

This helps make the case that the Milky Way only has two spiral arms; a commonly seen situation where a galaxy has a long central bar.

Original Source: NASA/JPL News Release

Despite their name, planetary nebulae have nothing to do with planets. They’re created when stars like our Sun enter the last stages of life, and puff off their outer layers. Then they shrink down to become a white dwarf star. This must have happened in the case of planetary nebula SuWt 2, located about 6,500 light-years away from Earth. Except there’s a problem: the white dwarf remnant has gone missing. The Hubble Space Telescope has been called in to help in the search, but so far, nothing has turned up.

The case of the missing white dwarf was announced today at the 212th meeting of the American Astronomical Society by astronomers from the Space Telescope Science Institute in Baltimore, and other British and American colleagues.

With most planetary nebulae, there are beautiful and delicate rings; the remnants puffed off by the dying star. There should also be a white dwarf star shining in the middle of the nebula.

At the center of SuWt 2, there two tightly bound stars orbiting one another in just 5 days – neither of these are white dwarfs. Both are hotter than our own Sun, but they’re not hot enough to actually make the nebula glow. To get the nebula as bright as it is, you need a bright source of ultraviolet radiation coming from a white dwarf. Once again… where did it go?

All the evidence points towards that binary pair of stars orbiting within the nebula. The astronomers think that there used to be three stars orbiting one another. The most massive star evolved into a red giant, which temporarily engulfed the other two stars. Trapped inside the red giant’s envelope, they slowed down and spiraled inward.

The spiraling stars caused the red giant’s envelope to spin up so fast that the outer layers were ejected into space, causing the beautiful rings of debris we see today. This might also help explain why the two stars are rotating more slowly than expected.

The exposed core of the red giant might have blasted out ultraviolet radiation that caused the nebula to glow. And then shortly after that, the red giant shrunk down to become a dim white dwarf – one that’s too faint to be detected, even by Hubble.

Original Source: Hubble News Release