Jupiter, the largest and most massive planet in our solar system, may be its own worst enemy. It turns out that its central core may in fact be self-destructing, gradually liquifying and dissolving over time. This implies it was previously larger than it is now, and may dissolve altogether at some point in the future. Will Jupiter eventually destroy itself completely? No, probably not, but it may lose its heart…
The core is composed of iron, rock and ice and weighs about ten times as much as Earth. That’s still small though, compared to the overall mass of Jupiter itself, which weighs as much as 318 Earths! The core is buried deep within the thick atmosphere of hydrogen and helium. Conditions there are brutal, with a temperature of about 16,000 kelvin – hotter than the surface of the Sun – and a pressure about 40 million times greater than the atmospheric pressure on Earth. The core is surrounded by a fluid of metallic hydrogen which results from the intense pressure deep down in the atmosphere. The bulk of Jupiter though is the atmosphere itself, hence why Jupiter (and Saturn, Uranus and Neptune) are called gas giants.
One of the primary ingredients in the rock of the core is magnesium oxide (MgO). Planetary scientists wanted to see what would happen when it is subjected to the conditions found at the core; they found that it had a high solubility and started to dissolve. So if it is in a state of dissolution, then it was probably larger in the past than it is now and scientists would like to understand the process. According to David Stevenson of the California Institute of Technology, “If we can do that, then we can make a very useful statement about what Jupiter was like at genesis. Did it have a substantial core at that time? If so, was it 10 Earth masses, 15, 5?”
The findings also mean that some exoplanets which are even larger and more massive than Jupiter, and thus likely even hotter at their cores, may no longer have any cores left at all. They would be indeed be gas giants in the most literal sense.
The conditions inside Jupiter’s core can’t be duplicated in labs yet, but the spacecraft Juno should provide much more data when it arrives at and starts orbiting Jupiter in 2016.
NASA’s Dawn Asteroid Orbiter successfully spiraled down today to the closest orbit the probe will ever achieve around the giant asteroid Vesta, and has now begun critical science observations that will ultimately yield the mission’s highest resolution measurements of this spectacular body.
“What can be more exciting than to explore an alien world that until recently was virtually unknown!” Dr. Marc Rayman gushed in an exclusive interview with Universe Today. Rayman is Dawn’s Chief Engineer from NASA’s Jet Propulsion Lab (JPL) in Pasadena, Calif., and a protégé of Star Trek’s Mr. Scott.
Before Dawn, Vesta was little more than a fuzzy blob in the world’s most powerful telescopes. Vesta is the second most massive object in the main Asteroid Belt between Mars and Jupiter.
Dawn is now circling about Vesta at the lowest planned mapping orbit, dubbed LAMO for Low Altitude Mapping Orbit. The spacecraft is orbiting at an average altitude of barely 130 miles (210 kilometers) above the heavily bombarded and mysterious world that stems from the earliest eons of our solar system some 4.5 Billion years ago. Each orbit takes about 4.3 hours.
“It is both gratifying and exciting that Dawn has been performing so well,” Rayman told me.
Dawn arrived in orbit at Vesta in July 2011 after a nearly 4 year interplanetary cruise since blasting off atop a Delta II rocket from Cape Canaveral, Florida in September 2007. The probe then spent the first few weeks at an initial science survey altitude of about 1,700 miles (2,700 kilometers).
Gradually the spaceship spiraled down closer to Vesta using her ion propulsion thrusters.
See Vesta science orbit diagram, below, provided courtesy of Dr. Marc Rayman.
Along the way, the international science and engineering team commanded Dawn to make an intermediate stop this past Fall 2011 at the High Altitude Mapping orbit altitude (420 miles, or 680 kilometers).
“It is so cool now to have reached this low orbit [LAMO]. We already have a spectacular collection of images and other fascinating data on Vesta, and now we are going to gain even more,” Rayman told me.
“We have a great deal of work ahead to acquire our planned data here, and I’m looking forward to every bit!
Dawn will spend a minimum of 10 weeks acquiring data at the LAMO mapping orbit using all three onboard science instruments, provided by the US, Germany and Italy.
While the framing cameras (FC) from Germany and the Visible and Infrared Mapping spectrometer (VIR) from Italy will continue to gather mountains of data at their best resolution yet, the primary science focus of the LAMO orbit will be to collect data from the gamma ray and neutron detector (GRaND) and the gravity experiment.
GRaND will measure the elemental abundances on the surface of Vesta by studying the energy and neutron by-products that emanate from it as a result of the continuous bombardment of cosmic rays. The best data are obtained at the lowest altitude.
By examining all the data in context, scientists hope to obtain a better understanding of the formation and evolution of the early solar system.
Vesta is a proto-planet, largely unchanged since its formation, and whose evolution into a larger planet was stopped cold by the massive gravitational influence of the planet Jupiter.
“Dawn’s visit to Vesta has been eye-opening so far, showing us troughs and peaks that telescopes only hinted at,” said Christopher Russell, Dawn’s principal investigator, based at UCLA. “It whets the appetite for a day when human explorers can see the wonders of asteroids for themselves.”
After investigating Vesta for about a year, the engineers will ignite Dawn’s ion propulsion thrusters and blast away to Ceres, the largest asteroid which may harbor water ice and is another potential outpost for extraterrestrial life
Dawn will be the first spaceship to orbit two worlds and is also the first mission to study the asteroid belt in detail.
Read continuing features about Dawn by Ken Kremer starting here:
[/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.
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.
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.
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.”
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 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.
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.
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.”
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.
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.
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
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.”
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.