Posted on by Tammy Plotner

Carbon “Super Earths” – Diamond Planets

Iron, carbon, and oxygen subjected to intense temperatures and pressures form a pocket of iron oxide (bottom, center) and a darker pocket of diamond (bottom, right). Electron micrograph courtesy of Ohio State University

[/caption]During a laboratory experiment at Ohio State University, researchers were simulating the pressures and conditions necessary to form diamonds in the Earth’s mantle when they came across a surprise… A carbon “Super Earth” could exist. While endeavoring to understand how carbon might behave in other solar systems, they wondered if planets high in this element could be pressurized to the point of producing this valuable gemstone. Their findings point to the possibility that the Milky Way could indeed be home to stars where planets might consist of up to 50% diamond.

The research team is headed by Wendy Panero, associate professor in the School of Earth Sciences at Ohio State, and doctoral student Cayman Unterborn. As part of their investigation they incorporated their findings from earlier experiments into a computer modeling simulation. This was then used to create scenarios where planets existed with a higher carbon content than Earth..

The result: “It’s possible for planets that are as big as fifteen times the mass of the Earth to be half made of diamond,” Unterborn said. He presented the study Tuesday at the American Geophysical Union meeting in San Francisco.

“Our results are striking, in that they suggest carbon-rich planets can form with a core and a mantle, just as Earth did,” Panero added. “However, the cores would likely be very carbon-rich – much like steel – and the mantle would also be dominated by carbon, much in the form of diamond.”

At the center of our planet is an assumed molten iron core, overlaid with a mantle of silica-based minerals. This basic building block of Earth is what condensed from the materials in our solar cloud. In an alternate situation, a planet could form in a carbon-rich environment, thereby having a different planet structure – and a different potential for life. (Fortunately for us, our molten interior provides geothermal energy!) On a diamond planet, the heat would dissipate quickly – leading to a frozen core. On this basis, a diamond planet would have no geothermal resources, lack plate tectonics and wouldn’t be able to support either an atmosphere or a magnetic field.

“We think a diamond planet must be a very cold, dark place,” Panero said.

How did they come up with their findings? Panero and former graduate student Jason Kabbes took a miniature sample of iron, carbon, and oxygen and subjected it to pressures of 65 gigapascals and temperatures of 2,400 Kelvin (close to 9.5 million pounds per square inch and 3,800 degrees Fahrenheit – conditions similar to the Earth’s deep interior). As they observed the experiment microscopically, they saw oxygen bonding with iron to create rust… but what was left turned to pure carbon and eventually formed diamond. This led them to wonder about planetary formation implications.

“To date, more than five hundred planets have been discovered outside of our solar system, yet we know very little about their internal compositions,” said Unterborn, who is an astronomer by training.

“We’re looking at how volatile elements like hydrogen and carbon interact inside the Earth, because when they bond with oxygen, you get atmospheres, you get oceans – you get life,” Panero said. “The ultimate goal is to compile a suite of conditions that are necessary for an ocean to form on a planet.”

But don’t confuse their findings with recent, unrelated studies which involves the remnants of an expired star from a binary system. The OSU team’s finding simply suggest this type of planet could form in our galaxy, but how many or where they might be is still very open to interpretation. It’s a question that’s being investigated by Unterborn and Ohio State astronomer Jennifer Johnson.

Because diamonds are forever…

Original Story Source: Ohio State Research News.

Posted on by Tammy Plotner

Asteroid Lutetia… A Piece Of Earth?

This image of the unusual asteroid Lutetia was taken by ESA’s Rosetta probe during its closest approach in July 2010. Lutetia, which is about 100 kilometres across, seems to be a leftover fragment of the same original material that formed the Earth, Venus and Mercury. It is now part of the main asteroid belt, between the orbits of Mars and Jupiter, but its composition suggests that it was originally much closer to the Sun. Credit: ESA 2010 MPS for OSIRIS Team MPS/UPD/LAM/IAA/RSSD/INTA/UPM/DASP/IDA

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According to data received from ESA’s Rosetta spacecraft, ESO’s New Technology Telescope, and NASA telescopes, strange asteroid Lutetia could be a real piece of the rock… the original material that formed the Earth, Venus and Mercury! By examining precious meteors which may have formed at the time of the inner Solar System, scientists have found matching properties which indicate a relationship. Independent Lutetia must have just moved its way out to join in the main asteroid belt…

A team of astronomers from French and North American universities have been hard at work studying asteroid Lutetia spectroscopically. Data sets from the OSIRIS camera on ESA’s Rosetta spacecraft, ESO’s New Technology Telescope (NTT) at the La Silla Observatory in Chile, and NASA’s Infrared Telescope Facility in Hawaii and Spitzer Space Telescope have been combined to give us a multi-wavelength look at this very different space rock. What they found was a very specific type of meteorite called an enstatite chondrite displayed similar content which matched Lutetia… and what is theorized as the material which dates back to the early Solar System. Chances are very good that enstatite chondrites are the same “stuff” which formed the rocky planets – Earth, Mars and Venus.

“But how did Lutetia escape from the inner Solar System and reach the main asteroid belt?” asks Pierre Vernazza (ESO), the lead author of the paper.

It’s a very good question considering that an estimated less than 2% of the material which formed in the same region of Earth migrated to the main asteroid belt. Within a few million years of formation, this type of “debris” had either been incorporated into the gelling planets or else larger pieces had escaped to a safer, more distant orbit from the Sun. At about 100 kilometers across, Lutetia may have been gravitationally influenced by a close pass to the rocky planets and then further affected by a young Jupiter.

“We think that such an ejection must have happened to Lutetia. It ended up as an interloper in the main asteroid belt and it has been preserved there for four billion years,” continues Pierre Vernazza.

Asteroid Lutetia is a “real looker” and has long been a source of speculation due to its unusual color and surface properties. Only 1% of the asteroids located in the main belt share its rare characteristics.

“Lutetia seems to be the largest, and one of the very few, remnants of such material in the main asteroid belt. For this reason, asteroids like Lutetia represent ideal targets for future sample return missions. We could then study in detail the origin of the rocky planets, including our Earth,” concludes Pierre Vernazza.

Original Story Source: ESO News Release.

Posted on by Ray Sanders

Was a Fifth Giant Planet Expelled from Our Solar System?

Artist’s impression of a fifth giant planet being ejected from the solar system. Image credit: Southwest Research Institute

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Earth’s place in the “Goldilocks” zone of our solar system may be the result of the expulsion of a fifth giant planet from our solar system during its first 600 million years, according to a recent journal publication.

“We have all sorts of clues about the early evolution of the solar system,” said author Dr. David Nesvorny of the Southwest Research Institute. “They come from the analysis of the trans-Neptunian population of small bodies known as the Kuiper Belt, and from the lunar cratering record.”

Nesvorny and his team used the clues they had to build computer simulations of the early solar system and test their theories. What resulted was an early solar system model that has quite a different configuration than today, and a jumbling of planets that may have given Earth the “preferred” spot for life to evolve.


Researchers interpret the clues as evidence that the orbits of Jupiter, Saturn, Uranus and Neptune were affected by a dynamical instability when our solar system was only about half a billion years old. This instability is believed to have helped increase the distance between the giant planets, along with scattering smaller bodies. The scattering of small bodies pushed objects both inward, and outward with some objects ending up in the Kuiper Belt and others impacting the terrestrial planets and the Moon. Jupiter is believed to have scattered objects outward as it moved in towards the sun.

One problem with this interpretation is that slow changes to Jupiter’s orbit would most likely add too much momentum to the orbits of the terrestrial planets. The additional momentum would have possibly caused a collision of Earth with Venus or Mars.

“Colleagues suggested a clever way around this problem,” said Nesvorny. “They proposed that Jupiter’s orbit quickly changed when Jupiter scattered off of Uranus or Neptune during the dynamical instability in the outer solar system.”

Basically if Jupiter’s early migration “jumps,” the orbital coupling between the terrestrial planets and Jupiter is weaker, and less harmful to the inner solar system.

Animation showing the evolution of the planetary system from 20 million years before the ejection to 30 million years after. Five initial planets are shown by red circles, small bodies are in green.
After the fifth planet is ejected, the remaining four planets stabilize after a while, and looks like the outer solar system in the end, with giant planets at 5, 10, 20 and 30 astronomical units.
Click image to view animation. Image Credit: Southwest Research Institute

Nesvorny and his team performed thousands of computer simulations that attempted to model the early solar system in an effort to test the “jumping-Jupiter” theory. Nesvorny found that Jupiter did in fact jump due to gravitational interactions from Uranus or Neptune, but when Jupiter jumped, either Uranus or Neptune were expelled from the solar system. “Something was clearly wrong,” he said.

Based on his early results, Nesvorny added a fifth giant planet, similar to Uranus or Neptune to his simulations. Once he ran the reconfigured simulations, everything fell into place. The simulation showed the fifth planet ejected from the solar system by Jupiter, with four giant planets remaining, and the inner, terrestrial planets untouched.

Nesvorny concluded with, “The possibility that the solar system had more than four giant planets initially, and ejected some, appears to be conceivable in view of the recent discovery of a large number of free-floating planets in interstellar space, indicating the planet ejection process could be a common occurrence.”

If you’d like to read Nesvorny’s full paper, you can access it at: http://arxiv.org/pdf/1109.2949v1

Source: Southwest Research Institute Press Release

Posted on by Ray Sanders

New ESA Images Reveal Volcanic History of Mars

Tharsis Tholus towers 8 km above the surrounding terrain. Its base stretches 155 x 125 km. What makes Tharsis Tholus unusual is its extremely battered condition. Image Credit: ESA/DLR/FU Berlin (G. Neukum)

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Earlier this week, The European Space Agency released new Mars images taken by instruments aboard the Mars Express spacecraft. The images show details of Tharsis Tholus, which appears to be a very large and extinct volcano that has been battered and deformed over time.

On Earth, Tharsis Tholus would be a towering giant of a volcano, looming 8 km above the surrounding terrain, with a base of roughly 155 x 125 km. Despite its size, Tharsis Tholus is just an average run-of-the-mill volcano on Mars. That being said, it isn’t the size of Tharsis Tholus that makes it interesting to scientists – what makes the remnants of this volcano stand out is its extremely battered condition.

What does the battered condition of Tharsis Tholus mean to planetary scientists studying Mars?

Details shown in the image above by the HRSC high-resolution stereo camera on ESA’s Mars Express spacecraft reveal signs of dramatic events which have significantly altered the volcanic region of Tharsis Tholus. Two (or more) large sections have collapsed around its eastern and western regions in the past several billion years, leaving signs of erosion and faulting.

One main feature of Tharsis Tholus that stands out is the volcanic caldera in its center. The caldera is nearly circular, roughly 30 km across and ringed by faults that have allowed the floor of the caldera to subside by nearly 3km. Planetary scientists believe the volcano emptied its magma chamber during eruptions. Once the magma chamber had emptied its lava onto the surface, the chamber roof became unstable under its own weight and collapsed, forming the large caldera.

This image was created using a Digital Terrain Model (DTM) obtained from the High Resolution Stereo Camera on ESA’s Mars Express spacecraft. Elevation data from the DTM is colour coded: purple indicates the lowest lying regions and beige the highest. Image Credit: ESA/DLR/FU Berlin (G. Neukum)

This month is a very busy month for Mars exploration. Russia’s recently launched (and in distress) Phobos mission (Mission coverage at: http://www.universetoday.com/90808/russians-race-against-time-to-save-ambitious-phobos-grunt-mars-probe-from-earthly-demise/) has a mission goal of returning a sample from Mars’ moon, Phobos, along with “piggyback” missions by China and the Planetary Society.

NASA’s plans to launch the Mars Science Laboratory on November 25th (Coverage at: http://www.universetoday.com/90639/curiosity-rover-bolted-to-atlas-rocket-in-search-of-martian-microbial-habitats/). MSL consists of the “Curiosity” rover and will be performing experiments designed to detect organic molecules, which may help detect signs of past or present life on Mars.

This month also marks the end of the “Mars500” mission, which ended on Friday (coverage at: http://www.universetoday.com/90554/mars500-crew-ready-to-open-hatch/ when the participants opened their hatch for the first time since June 2010. During the past 520 days, the participants were working in a simulated spacecraft environment in Moscow.

Learn more about Mars Express at: http://www.esa.int/esaMI/Mars_Express/index.html

Source: ESA Press Release

Posted on by Tammy Plotner

Did A Supernova Shape Our Solar System?

The time evolution of case I. Color coded is the density at t = 0 kyr, t = 4.16 kyr and t = 8.33 kyr. The length scale is given in units of the radius of the initial cold core (R0 = 0.21 pc). Credit: M. Gritschneder (et al)

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Away in space some 4.57 billion years ago, in a galaxy yet to be called the Milky Way, a hydrogen molecular cloud collapsed. From it was born a G-type main sequence star and around it swirled a solar nebula which eventually gelled into a solar system. But just what caused the collapse of the molecular cloud? Astronomers have theorized it may have been triggered by a nearby supernova event… And now new computer modeling confirms that our Solar System was born from the ashes a dead star.

While this may seem like a cold case file, there are still some very active clues – one of which is the study of isoptopes contained within the structure of meteorites. As we are well aware, many meteorites could very well be bits of our primordial solar nebula, left virtually untouched since they formed. This means their isotopic signature could spell out the conditions that existed within the molecular cloud at the time of its collapse. One strong factor in this composition is the amount of aluminium-26 – an element with a radioactive half-life of 700,000 years. In effect, this means it only takes a relatively minor period of time for the ratio between Al-26 and Al-24 to change.

“The time-scale for the formation events of our Solar System can be derived from the decay products of radioactive elements found in meteorites. Short lived radionuclides (SLRs) such as 26Al , 41Ca, 53Mn and 60Fe can be employed as high-precision and high-resolution chronometers due to their short half-lives.” says M. Gritschneder (et al). “These SLRs are found in a wide variety of Solar System materials, including calcium-aluminium-rich inclusions (CAIs) in primitive chondrites.”

However, it would seem that a class of carbonaceous chondrite meteorites known CV-chondrites, have a bit more than their fair share of Al-26 in their structure. Is it the smoking gun of an event which may have enriched the cloud that formed it? Isotope measurements are also indicative of time – and here we have two examples of meteorites which formed within 20,000 years of each other – yet are significantly different. What could have caused the abundance of Al-26 and caused fast formation?

“The general picture we adopt here is that a certain amount of Al-26 is injected in the nascent solar nebula and then gets incorporated into the earliest formed CAIs as soon as the temperature drops below the condensation temperature of CAI minerals. Therefore, the CAIs found in chondrites represent the first known solid objects that crystalized within our Solar System and can be used as an anchor point to determine the formation time-scale of our Solar System.” explains Gritschneder. “The extremely small time-span together with the highly homogeneous mixing of isotopes poses a severe challenge for theoretical models on the formation of our Solar System. Various theoretical scenarios for the formation of the Solar System have been discussed. Shortly after the discovery of SLRs, it was proposed that they were injected by a nearby massive star. This can happen either via a supernova explosion or by the strong winds of a Wolf-Rayet star.”

While these two theories are great, only one problem remains… Distinguishing the difference between the two events. So Matthias Gritschneder of Peking University in Beijing and his colleagues set to work designing a computer simulation. Biased towards the supernova event, the model demonstrates what happens when a shockwave encounters a molecular cloud. The results are an appropriate proportion of Al-26 – and a resultant solar system formation.

“After discussing various scenarios including X-winds, AGB stars and Wolf-Rayet stars, we come to the conclusion that triggering the collapse of a cold cloud core by a nearby supernova is the most promising scenario. We then narrow down the vast parameter space by considering the pre-explosion survivability of such a clump as well as the cross-section necessary for sufficient enrichment.” says Gritschneder. “We employ numerical simulations to address the mixing of the radioactively enriched SN gas with the pre-existing gas and the forced collapse within 20 kyr. We show that a cold clump at a distance of 5 pc can be sufficiently enriched in Al-26 and triggered into collapse fast enough – within 18 kyr after encountering the supernova shock – for a range of different metallicities and progenitor masses, even if the enriched material is assumed to be distributed homogeneously in the entire supernova bubble. In summary, we show that the triggered collapse and formation of the Solar System as well as the required enrichment with radioactive 26Al are possible in this scenario.”

While there are still other isotope ratios yet to be explained and further modeling done, it’s a step toward the future understanding of how solar systems form.

Original Story Source: MIT Technology Review News Release. For Further Reading: The Supernova Triggered Formation And Enrichment Of Our Solar System.

Posted on by Ray Sanders

Are Black Holes Planet Smashers?

Light echo of dust illuminated by nearby star V838 Monocerotis as it became 600,000 times more luminous than our Sun in January 2002. Credit: NASA/ESA

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Some supermassive black holes are obscured by oddly shaped dust clouds which resemble doughnuts. These clouds have been an unsolved puzzle, but last week a scientist at the University of Leicester proposed a new theory to explain the origins of these clouds, saying that they could be the results of high-speed collisions between planets and asteroids in the central region of galaxies, where the supermassive black holes reside.

While black holes are a death knell for any objects wandering too close, this may mean even planets in a region nearby a black hole are doomed — but not because they would be sucked in. The central regions of galaxies just may be mayhem for planets.

“Too bad for life on these planets, ” said Dr. Sergei Nayakshin, whose paper will be published in the Monthly Notices of the Royal Astronomical Society journal.

In the center of nearly all galaxies are supermassive black holes. Previous studies show that about half of supermassive black holes are obscured by dust clouds.

Nayakshin and his team found inspiration for their new theory from our Solar System, and based their theory on the zodiacal dust which is known to originate from collisions between solid bodies such as asteroids and comets.

The central point of Nayakshin’s theory is that not only are black holes present in the central region of a galaxy, but stars, planets and asteroids as well.

The team’s theory asserts that any collisions between planets and asteroids in the central region of a galaxy would occur at speeds of up to 1000 km/sec. Given the tremendous speeds and energy present in such collisions, eventually rocky objects would be pulverized into microscopic dust grains.

Nayakshin also mentioned that the central region of a galaxy is an extremely harsh environment, given high amounts of deadly radiation and frequent collisions, both of which would make any planets near a supermassive black hole inhospitable well before they were destroyed in any collisions.

While Nayakshin said the frequent collisions would be bad news for any life that may exist on the planets, he added, “On the other hand the dust created in this way blocks much of the harmful radiation from reaching the rest of the host galaxy. This in turn may make it easier for life to prosper elsewhere in the rest of the central region of the galaxy.”

Nayakshin believes that a greater understanding of the origins of the dust near black holes is important to better understand how black holes grow and affect their host galaxy, and concluded with, “We suspect that the supermassive black hole in our own Galaxy, the Milky Way, expelled most of the gas that would otherwise turn into more stars and planets. Understanding the origin of the dust in the inner regions of galaxies would take us one step closer to solving the mystery of the supermassive black holes.”

Source: University of Leicester Press Release

Posted on by Ken Kremer

Russia Fuels Phobos-Grunt and sets Mars Launch for November 9

The Phobos-Grunt spacecraft is scheduled blastoff on November 9, 2011 from Baikonur Cosmodrome. It will reach Mars orbit in 2012 and eventually land on Phobos and return the first ever soil samples back to Earth in 2014. Credit Roscosmos

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Russia’s Space Agency, Roscosmos, has set November 9 as the launch date for the Phobos-Grunt mission to Mars and its tiny moon Phobos. Roscosmos has officially announced that the audacious mission to retrieve the first ever soil samples from the surface of Phobos will blastoff from the Baikonur Cosmodrome in Kazakhstan atop a Zenit-2SB rocket at 00:16 a.m. Moscow time.

Roscosmos said that engineers have finished loading all the propellants into the Phobos-Grunt main propulsion module (cruise stage), Phobos lander and Earth return module at Facility 31 at Baikonur.

Phobos-Grunt is Russia’s first mission to Mars in almost two decades and a prelude to an ambitious program of even more interplanetary Russian science flights.

Russian Phobos-Grunt spacecraft is set to launch to Mars on November 9, 2011.
L-shaped soil sample transfer tube extends from Earth return module ( top -yellow) and solar panel to bottom (left) of lander module. 2 landing legs, communications antenna, sampling arm, propulsion tanks and more are visible. Credit Roscosmos

Technicians also fueled the companion Yinghou-1 mini-satellite, provided by China, that will ride along inside a truss segment between the MDU propulsion module and the Phobos-Grunt lander.

The 12,000 kg Phobos-Grunt interplanetary spacecraft is being moved to an integration and test area at Facility 31 for integration with the departure segments of the Zenit rocket.

The next step is to enclose Phobos-Grunt inside the protective payload fairing and transport it to Facility 42 for mating atop the upper stage of the stacked Zenit-2SB booster rocket.

After about an 11 month journey, the spaceship will enter Mars orbit and spend several months searching for a suitable landing site on Phobos. The goal of the bold mission is to retrieve up to 200 grams of soil and rock from Phobos and return them to Earth in August 2014. The samples will help unlock the mysteries of the origin and evolution of Phobos, Mars and the Solar System.

Scientists hope that bits of Martian soil will be mixed in with Phobos soil.

Phobos-Grunt is equipped with a powerful 50 kg payload of some 20 international science instruments.

The 110 kg Yinghou-1, which translates as Firefly-1, is China’s first spaceship to voyage to Mars. It will be jettisoned by Phobos-Grunt into a separate orbit about Mars. The probe will photograph the Red planet with two cameras and study it with a magnetometer to explore Mars’ magnetic field and science instruments to explore its upper atmosphere.

Earth’s other mission to Mars in 2011, NASA’s Curiosity rover, is set to blast off for Mars on Nov. 25

Labeled Schematic of Phobos-Grunt and Yinghou-1 (YH-1) orbiter

Read Ken’s continuing features about Russia’s Phobos-Grunt Mars mission here::
Phobos-Grunt and Yinghou-1 Arrive at Baikonur Launch Site to tight Mars Deadline
Phobos-Grunt: The Mission Poster
Daring Russian Sample Return mission to Martian Moon Phobos aims for November Liftoff

Read Ken’s continuing features about Curiosity starting here:
Curiosity Buttoned Up for Martian Voyage in Search of Life’s Ingredients
Assembling Curiosity’s Rocket to Mars
Encapsulating Curiosity for Martian Flight Test
Dramatic New NASA Animation Depicts Next Mars Rover in Action

Posted on by Nancy Atkinson

Herschel Observatory Detects ‘Oceans’ of Water Around Distant Star

Detection of water vapour in the spectrum of TW Hydrae's protoplanetary disc. Credits: ESA/NASA/JPL-Caltech/M. Hogerheijde (Leiden Observatory)

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There’s enough water in a planet-forming disk around a distant star to fill several thousand Earth oceans, according to new observations with the Herschel space observatory. Astronomers have found evidence of water vapor originating from ice on dust grains in the disc around a young star, TW Hydrae. The star is between 5-10 million years old, so is in its final stages of formation.

“The detection of water sticking to dust grains throughout the disc would be similar to events in our own Solar System’s evolution, where over millions of years, similar dust grains then coalesced to form comets,” said Michiel Hogerheijde of Leiden University in the Netherlands, who led the study. “These comets we believe became a contributing source of water for the planets.”

Herschel has found water around other stars, such as an old red giant star CW Leonis, and other telescopes like Spitzer have also observed abundant water in nascent planet forming regions around other stars.

But scientists say this latest research from Herschel breaks new ground in understanding water’s role in planet-forming discs and gives scientists a new testing ground for looking at how water came to our own planet.

“With Herschel we can follow the trail of water through all the steps of star and planet formation,” said Göran Pilbratt, Herschel Project Scientist at ESA.

Scientists think the water vapor signature is produced when the ice coated dust grains are warmed by interstellar UV radiation.

Read more on this discovery at the ESA Herschel website.

Posted on by Ray Sanders

How Did Jupiter Shape Our Solar System?

Shortly after forming, Jupiter was slowly pulled toward the sun. Saturn was also pulled in and eventually, their fates became linked. When Jupiter was about where Mars is now, the pair turned and moved away from the sun. Scientists have referred to this as the "Grand Tack," a reference to the sailing maneuver. Credit: NASA/GSFC

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Jupiter hasn’t always been in the same place in our solar system. Early in the history of our solar system, Jupiter moved inward towards the sun, almost to where Mars currently orbits now, and then back out to its current position.

The migration through our solar system of Jupiter had some major effects on our solar system. Some of the effects of Jupiter’s wanderings include effects on the asteroid belt and the stunted growth of Mars.

What other effects did Jupiter’s migration have on the early solar system and how did scientists make this discovery?

In a research paper published in the July 14th issue of Nature, First author Kevin Walsh and his team created a model of the early solar system which helps explain Jupiter’s migration. The team’s model shows that Jupiter formed at a distance of around 3.5 A.U (Jupiter is currently just over 5 A.U from the sun) and was pulled inward by currents in the gas clouds that still surrounded the sun at the time. Over time, Jupiter moved inward slowly, nearly reaching the same distance from the sun as the current orbit of Mars, which hadn’t formed yet.

“We theorize that Jupiter stopped migrating toward the sun because of Saturn,” said Avi Mandell, one of the paper’s co-authors. The team’s data showed that Jupiter and Saturn both migrated inward and then outward. In the case of Jupiter, the gas giant settled into its current orbit at just over 5 a.u. Saturn ended its initial outward movement at around 7 A.U, but later moved even further to its current position around 9.5 A.U.

Astronomers have had long-standing questions regarding the mixed composition of the asteroid belt, which includes rocky and icy bodies. One other puzzle of our solar system’s evolution is what caused Mars to not develop to a size comparable to Earth or Venus.

Artist's conception of early planetary formation from gas and dust around a young star. Image Credit: NASA/JPL-Caltech

Regarding the asteroid belt, Mandell explained, “Jupiter’s migration process was slow, so when it neared the asteroid belt, it was not a violent collision but more of a do-si-do, with Jupiter deflecting the objects and essentially switching places with the asteroid belt.”

Jupiter’s slow movement caused more of a gentle “nudging” of the asteroid belt when it passed through on its inward movement. When Jupiter moved back outward, the planet moved past the location it originally formed. One side-effect of caused by Jupiter moving further out from its original formation area is that it entered the region of our early solar system where icy objects were. Jupiter pushed many of the icy objects inward towards the sun, causing them to end up in the asteroid belt.

“With the Grand Tack model, we actually set out to explain the formation of a small Mars, and in doing so, we had to account for the asteroid belt,” said Walsh. “To our surprise, the model’s explanation of the asteroid belt became one of the nicest results and helps us understand that region better than we did before.”

With regards to Mars, in theory Mars should have had a larger supply gas and dust, having formed further from the sun than Earth. If the model Walsh and his team developed is correct, Jupiter foray into the inner solar system would have scattered the material around 1.5 A.U.

Mandell added, “Why Mars is so small has been the unsolvable problem in the formation of our solar system. It was the team’s initial motivation for developing a new model of the formation of the solar system.”

An interesting scenario unfolds with Jupiter scattering material between 1 and 1.5 AU. Instead of the higher concentration of planet-building materials being further out, the high concentration led to Earth and Venus forming in a material-rich region.

The model Walsh and his team developed brings new insight into the relationship between the inner planets, our asteroid belt and Jupiter. The knowledge learned not only will allow scientists to better understand our solar system, but helps explain the formation of planets in other star systems. Walsh also mentioned, “Knowing that our own planets moved around a lot in the past makes our solar system much more like our neighbors than we previously thought. We’re not an outlier anymore.”

If you’d like to access the paper (subscription or paid/university access required), you can do so at: http://www.nature.com/nature/journal/v475/n7355/full/nature10201.html

Source: NASA Solar System News, Nature

Posted on by Tammy Plotner

Cosmic Collisions Could Eject Habitable Planets

One of 42 new proplyds discovered in the Orion Nebula, 177-341E is one of the bright proplyds that lies relatively close to the nebula’s brightest star, Theta 1 Orionis C. The tadpole-shaped tail is actually a jet of matter flowing away from the excited cusp. Credit:NASA/ESA and L. Ricci (ESO)

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When it comes to solar systems, chances are good that we’re a lot more special than we thought. According to a German-British team led by Professor Pavel Kroupa of the University of Bonn, our orderly neighborhood of varied planet sizes quietly orbiting in a nearly circular path isn’t a standard affair. Their new models show that habitable planets might just get ejected in a violent scenario where forming solar systems mean highly inclined orbits where hot Jupiters rule.

Some 4600 million years ago, our local planetary system was surmised to have evolved from a blanket of dust surrounding a rather ordinary star. Its planets orbited the same direction as the solar spin and lined up neatly on a plane fairly close to the solar equator. We were good little children… But maybe other systems aren’t so hospitable. There could be systems where the planets cruise around in the opposite direction of their host star’s spin – and have highly inclined orbits. What could cause one protoplanetary disk to take on quiet properties while another is more radical? Try a cosmic crash.

This new study focuses on the theory of a protoplanetary disk colliding with another cloud of material… not unrealistic thinking since most stars form within a cluster. The results could mean the inclusion of up to thirty times the mass of Jupiter. This added “weight” of extra gas and dust could add a tilt to a forming system. Team member Dr Ingo Thies, also of the University of Bonn, has carried out computer simulations to test the new idea. What he has found is that adding extra material can not only incline a forming disk, but cause a reverse spin as well. It may even speed up the planetary formation, leaving the rogues in retrograde orbits. This inhospitable scenario means that smaller planets get ejected systematically, leaving only hot Jupiters to hug in close to the parent star. Thankfully our path was a bit less disturbing.

Says Dr Thies: “Like most stars, the Sun formed in a cluster, so probably did encounter another cloud of gas and dust soon after it formed. Fortunately for us, this was a gentle collision, so the effect on the disk that eventually became the planets was relatively benign. If things had been different, an unstable planetary system may have formed around the Sun, the Earth might have been ejected from the Solar System and none of us would be here to talk about it.”

Professor Kroupa sees the model as a big step forward. “We may be on the cusp of solving the mystery of why some planetary systems are tilted so much and lack places where life could thrive. The model helps to explain why our Solar System looks the way it does, with the Earth in a stable orbit and larger planets further out. Our work should help other scientists refine their search for life elsewhere in the Universe.”

Original News Source: Royal Astronomical Society News.