Posted on by Fraser Cain

Was There a Planet Between Mars and Jupiter?

Main Belt Asteroids
Ceres, the recently promoted dwarf planet in the asteroid belt is still too small to be easily seen by Hubble credit: NASA/ESA/STScI

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.

Posted on by Jerry Coffey

Does Mars Have Rings?

Martian moon Phobos

Recently, while discussing what she had learned in class, my daughter asked me: ”does Mars have rings?”. She is ten and it is fun to see her interested in anything educational. Unfortunately, I had to tell her that no, Mars does not have rings. While saying no was disappointing, it left a good opportunity to teach her how planetary rings are formed..

Planetary ring systems are formed in two ways. The first is by ice and dust like those around the ice giants and similar to the rings around Saturn. Scientist believe that the particle have been captured by a planet’s gravity and are prevented from combining into a moon by that gravity. The rings are visible because of the light that the particles reflect. In the case of Saturn, some of the moons within the rings system have ice geysers that some scientist think are constantly replenishing the rings.

A second way that a planetary ring may form is through impact. If a large enough asteroid were to impact a planet, dust and rock debris would be thrown into space. That debris would then be captured by the planet’s gravity. Scientists believe that the debris will fall back to the planet, but do not know how long it would take.

Mars may develop a ring system in the future. Scientists know that Mar’s moon, Phobos, is in a decaying orbit around the planet. In anywhere from 10 million to 100 million years it will crash into the planet forming a ring system as the debris is ejected back into space. After a million or so years, that ring system will collapse back onto the planet’s surface, causing an extensive crater field.

That begs the question of how did Phobos find itself in such a predicament. Well, it is most likely a captured asteroid. Its orbit took it too close to Mars and it did not have enough velocity to escape the planet’s gravity. Many moons in our Solar System have come to orbit their primaries in this fashion. Usually, small moons are captured and large moons form in situ, so to speak.

Now you know the answer to ”does Mars have rings?” and a little about a rings in the planet’s future. Don’t forget to read up on Mar’s other moon Deimos and maybe look a little deeper into Phobos. If planetary rings interest you, NASA has plenty of information on their website.

Here’s an article the describes how Phobos will eventually crash into Mars. And here’s some more information about what Saturn’s rings are made of.

The Planetary Rings Node has many resources for Saturn’s rings. And here’s an article about potential rings around Pluto.

We’ve covered Mars in the past at Astronomy Cast. Episode 52: Mars, and Episode 91: The Search for Water on Mars. We also talk about Saturn’s rings in Episode 59: Saturn.

Sources:
http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/981027a.html
http://solarsystem.nasa.gov/planets/profile.cfm?Object=Mar_Phobos
http://apod.nasa.gov/apod/ap080414.html

Posted on by Fraser Cain

Pictures of Planet Mars

Mars, just a normal planet. No mystery here... (NASA/Hubble)

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.

Posted on by Jerry Coffey

Volcanoes on Mars

Olympus Mons. Image credit: NASA/JPL

There are many volcanoes on Mars. So many, that the planet is broken down into volcanic provinces for easier reference. Quite a few of them are very large because the planet has not had tectonic plate action for billions of years, so a single hotspot could flow unabated for millenia.

Olympus Mons is a shield volcano on Mars and it is the largest volcano in the Solar System. Located in the Tharsis region of the planet along with three other large volcanoes, Olympus Mons measures an incredible 27 km in height and is 3 times taller than Mount Everest. It is about 500 km in diameter. The mountain was formed from a single hotspot that flowed for thousands, if not millions, of years. The lack of plate tectonics that allowed this unhindered flow also prevented massive pressure buildups that would have blown the top off of the volcano, decreasing its overall height.

In the northern part of the Tharsis volcanic province is Alba Mons also known as Alba Patera. It is a unique volcanic structure for several reasons. The volcano features unnaturally low slopes formed by numerous and extensive lava flows. Its slopes are a mere 0.5 degrees. It has a double caldera feature with the central figure being 350 km wide and 1.5 km high. Flows from Alba Mons seem to extend 2,000 km north-south and 3,000 km east-west. The widespread flows make this one of the largest volcanoes in the Solar System by area. Some scientist point to the volcano’s antipodal location to the Hellas impact basin as a possible reason its formation. Seismic waves from the impact may have traveled through the planet causing a weakening of the crust at the point of origin for Alba Mons.

In the Elysium volcanic province there are three main volcanoes. The province covers an area that is about 2,000 km in diameter. The main volcanoes are Elysium Mons, Hecates Tholus, and Albor Tholus. The northwestern edge of the province is characterized by large channels that emerge from several valleys(grabens) on the flanks of Elysium Mons. The grabens may have formed from the subsurface release of large volumes of ground water. The channels are accompanied by associated sedimentary deposits possibly formed by mudflows. Elysium Mons is 375 km across and 14 km high. Hecates Tholus is 180 km across and 4.8 km high. Albor Tholus, the southern-most of the Elysium volcanoes, is 150 km in diameter and 4.1 km high.

There are many interesting volcanoes on Mars. The NASA source listed below will take you to a list of there Martian volcanoes and many details about each. Good luck with your research.

Here’s a Universe Today article about an ancient Mars volcano caldera, and information that volcanoes were active on Mars recently.

Here’s a cool slideshow of volcanoes on Mars, and more information about volcanism on Mars.

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
Wikipedia

Posted on by Nicholos Wethington

Map of Milky Way Redrawn (again)

Just yesterday Fraser wrote about the Milky Way’s demotion from a 4-arm spiral galaxy to a 2-arm. This isn’t the only change we’ll have to accept about our home galaxy: a Milky Way mapping project has discovered stars in the galaxy moving slower and in more elliptical orbits than predicted. This means we might have to redraw the map we have of our own neighborhood yet again.

Astronomers using the Very Long Baseline Array (VLBA) – a collaboration of ten radio telescopes across the United States – tracked the positions of masers in a dozen star-forming regions in the Milky Way. They used parallax to determine the distance to the masers, then combined this information with how the masers shifted in the plane of the sky, giving a 3-dimensional model of their movement.

Drawing a map of the Milky Way is a challenging task, as we only have an edge-on view of the galaxy in which we reside. To top it off, it’s full of dust and gas that muck up the view in the visible light spectrum. Using the VLBA’s radio antennae, though, has made it possible to track radio-emitting bodies as they move across the sky because radio waves travel more easily through matter than does light. Since the VLBA functions as one huge telescope, it can track the position of stars with great accuracy.

“Right now, our map of the Milky Way still has large areas marked ‘Here there be dragons.’ Ten years from now, those areas will be filled in,” said Mark Reid, of the Harvard-Smithsonian Center for Astrophysics. Reid presented these findings at a press conference at the 212th American Astronomical Society meeting.

Instead of neatly circling the galactic center, the stars mapped by Reid and his colleagues are tracing an elliptical orbit. Previous maps of the Milky Way have assumed that the material in our galaxy orbits the center in a circular fashion, so stars that don’t follow this path come as somewhat of a surprise.

The stars are moving slower likely because of the loss of angular momentum when they interact gravitationally with other matter in the galaxy, traveling through what is called a ‘density wave’. The best description of a density wave I’ve run across has to be Phil Plait’s over at Bad Astronomy:

If you were in a helicopter over a traffic jam on the freeway, it would look like the jam is a permanent fixture of the traffic. But in reality, cars leave the jam at the same rate as cars entering it. So while the jam itself stays put, the cars making it up always change. So it is with spiral arms: they are places where the matter in the galaxy is compressed, but stars enter the jam and stars leave. The arm looks permanent, but over time its resident stars, gas, and dust change

This probably won’t be the last time the map of the Milky Way gets edited. The European Space Agency’s Gaia satellite is set to launch in 2011, and will provide a 3-dimensional map of 1 billion stars located as far as 30,000 light-years away from Earth.

Source: CfA Press Release

Posted on by Fraser Cain

Mars Formation

As with the rest of the planets in the Solar System, Mars is believed to have formed out of the primitive solar nebula 4.5 billion years ago.

Instead of condensing directly, from dust particles to planet, Mars and the rest of the terrestrial planets probably started out as a collection of small particles. Dust particles clumped together to form larger and larger objects. Dust became sand, pebbles, rocks, asteroids, and eventually planetoids. The formation of Mars happened when these particles all came together.

The energy from all these collisions heated up planet Mars, giving it a molten core and volcanic activity. We can see evidence of the end of the planetary formation period because of the impact craters strewn across the surface of the planet. This period was called the late heavy bombardment period, and all the planets in the Solar System were devastated too.

Astronomers think that Mars is relatively small because Jupiter finished its own formation a little earlier, and scooped up most of the available material. The gravity from Jupiter also seems to have prevented the formation of another planet in between Mars and Jupiter; instead, we’ve just got the asteroid belt.

Although Mars doesn’t have active plate tectonics, and its volcanism ended millions of years ago, the planet is much more similar to Earth and Venus, and different to the Moon and Mercury. Mars is the only other world in the Solar System that has a transparent atmosphere, and surface conditions that could be considered somewhat habitable.

Here’s an article from Universe Today about why Mars might be so dry. And more information about where the water went on Mars.

Additional information about the history and formation of Mars. And even more information here.

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.

Posted on by Nancy Atkinson

Recipe for Giant Lunar Telescopes

Moon dust. Credit: NASA

Someone has finally figured out something useful for all the dust on the moon’s surface: mix it with some epoxy and a pinch of carbon to create giant telescope mirrors. “We could make huge telescopes on the moon relatively easily, and avoid the large expense of transporting a large mirror from Earth,” said Peter Chen at a press conference today at the American Astronomical Society meeting. “Since most of the materials are already there in the form of dust, you don’t have to bring very much stuff with you, and that saves a ton of money.”

Chen and is team had been working with carbon-fiber composite materials to produce high-quality telescope mirrors. But then they decided to try an experiment. They substituted tiny carbon nanotubes for the carbon-fiber composites, and mixed in epoxies with crushed rock that has the same
composition and grain size as lunar dust, they discovered to their surprise that they had created a very strong material with the consistency of concrete. This material can be used instead of glass to
make mirrors.

Then they spun their concoction at room temperature to create a 12-inch-wide telescope mirror form, which they then coated with aluminum to create a highly reflective surface.

“Our method could be scaled-up on the moon, using the ubiquitous lunar dust, to create giant telescope mirrors up to 50 meters in diameter,” said collaborator Douglas Rabin. Currently the world’s largest optical telescope is the 10.4-meter Gran Telescopio Canarias in the Canary Islands, so this would be quite a step up.

Like liquid mirror telescopes, these large telescopes on the moon have definite advantages. With a stable platform, and no atmosphere to absorb or blur starlight, the monster scope could record the spectra of extra solar terrestrial planets and detect atmospheric biomarkers such as ozone and methane. Two or more such telescopes spanning the surface of the Moon can work together to take direct images of Earth-like planets around nearby stars and look for brightness variations that come from oceans and continents.

“Constructing giant telescopes provides a strong rationale for doing astronomy from the moon,” says Chen. “We could also use this on-site composite material to build habitats for the astronauts, and mirrors to collect sunlight for solar-power farms.”

Posted on by Jerry Coffey

Orbit of Mars

The eccentricity in Mars' orbit means that it is . Credit: NASA

The orbit of Mars is the second most eccentric in the Solar System. Only Mercury’s orbit is more eccentric. At perihelion Mars is 206,655,215 km from the Sun and at aphelion it is 249,232,432 km distant. That is a variation of of just under 42,600,000 km. The average distance from Mars to the Sun (called the semi-major axis) is 228 million km. It takes Mars approximately 687 Earth days to complete on orbit. The orbit of a planet varies in relation to the gravitational influences of the bodies around it, so the eccentricity can change over time. AS recently as 1.35 million years ago, Mars was in a nearly circular orbit.

Mars, like all planets in the Solar System, is tilted along its axis(axial tilt). For Mars, the axial tilt is about 25.19 degrees. This tilt is similar to Earth’s, so Mars has seasons like ours. The Martian seasons are longer because a year on Mars is nearly twice as long as an Earth year. The dramatically changing distances between Mars’ aphelion and perihelion means that the seasons aren’t balanced like Earth. Mars is at its closest when its southern hemisphere is tilted towards the Sun. So the southern hemisphere experiences hotter summers than the northern hemisphere.

The orbit of Mars allows it to approach Earth at varying distances. It is easiest to observe when it is at its closest approach. Opposition occurs when Mars’ geocentric longitude is 180° different from the Sun’s. Opposition can occur as much as 8½ days before or after closest approach. The distance at close approach varies between about 54 and 103 million km due to their position in their orbits. The last Mars opposition was on January 29, 2010. The next will be on March 3, 2012(about 100 million km). The average time between the successive oppositions(synodic period) of Mars is 780 days. Mars made its closest approach to Earth in nearly 60,000 years(55,758,006 km) on August 27, 2003. While this was a record, it was only slightly closer than other close approaches.

The orbit of Mars is well understood and has been observed, and documented, for thousands of years. The planet’s short period of apparent retrograde motion was noted as early as 1534 B.C. After reading and understanding the planet’s orbit, you should research more about its atmosphere, gravity, and exploration. Only then will you have a grasp of a few of the mysteries surrounding the Red Planet.

Here’s an article about Martian ice ages in the past, related to tilt, and another about mid-latitude glaciers on Mars.

Here’s more general information about Mars. And here are some pages from NASA about the Mars Phoenix Lander mission.

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.

Source:
NASA

Posted on by Jerry Coffey

Mars is Named After…

Mars is named after the Roman god of war. Many believe that ancient peoples associated Mars with bloodshed and war because of its red color. The Romans were not the only society to associate the planet with bloodshed. The ancient Babylonians called it Nergal, after their god of fire, war, and destruction. In keeping with the planet’s association with the god Mars, its symbol is a circle with an arrow pointing outwards from its right corner. This is meant to represent Mar’s shield and spear.

That information is not nearly enough to satisfy anyone’s interest in the Red Planet, so here are a few interesting facts about Mars and its environs.

The largest mountain in the Solar System is on Mars. Olympus Mons is 27 km tall. It is a shield volcano that was able to erupt for million of years because Mars does not have tectonic plate movement. This allowed the same volcanic hotspot to erupt undisturbed until the giant mountain was formed.

The chemical symbol for iron is the same as the astronomical symbol for Mars. This is fitting, since the planet gets its reddish appearance from the iron oxide in the dust on its surface.

A year on Mars lasts 686.98 Earth days or 1.88 Earth years. There are four seasons throughout the year like here on Earth, but each season is longer than a typical Earth season.

Mars is full of water. Not liquid water like we see here on Earth, but water ice under the surface and at the bottom of craters. There is even evidence that there may be ice inside of caves on the Martian surface. These deposits are safe from the solar radiation that bombards the surface, so they are able to stay in place.

Mars does not have a magnetic field at this time, but spacecraft have detected residual magnetism in rocks on the surface. That would suggest an active magnetic field millions, if not billions, of years ago. Scientist believe that the core of Mars has become too solid to rotate and is no longer capable of generating a dynamo effect. A dynamo effect is essential in producing a magnetic field.

These are just a few of the interesting facts beyond who Mars is named after. Pay special attention to information generated by the Mars Express spacecraft. It has turned up a great deal of interesting data on, and under, the Martian surface.

In case you’re wondering, here’s how Jupiter got its name.

Here’s some historical information on Mars, the god of war, and more on Ares, the Greek version of Mars.

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
Case Western Reserve University – Astronomy

Posted on by Fraser Cain

The Face 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