A new NASA webpage allows you to see – as well as share – the changing seasons here on Earth. From space, NASA satellites record the change of seasons, which scientists study regional patterns on Earth. These images also help show bigger changes that may occur over many years, and the slide show, “The Change of Seasons: Views from Space,” shows some of the ways seasonal change affects our planet, and invites you to share your own photos of seasonal change where you live.
Caused by the tilt of Earth’s axis relative to its orbital plane around the sun, seasons have profound changes on our weather and climate. When seasons change, nature reacts differently, depending on location. Temperatures change, rain or snow falls, rivers may flood, to name just a few effects. See the changes in action at the “Change of Seasons” webpage.
The mid-section of the US got a dose of winter weather, as seen in this satellite image from NASA's Terra spacecraft, taken on Dec. 7, 2010. Credit: NASA
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OK, let’s duke it out. Who had it worse this past week as far as wintery weather: the entire United Kingdom, or the middle part of the United States? We’ll the the satellite images tell story.
The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite acquired the image above on December 7, two days after the weekend snow storm. A swath of white defines the path of the storm from Minnesota to Kentucky in the image. Weather predictions look there is more on the way this weekend.
And for the UK:
The UK covered in snow, as seen on Dec. 8, 2010. Credit: NASA's Aqua satellite.
Snow and clouds present an almost uniform white to this satellite image. Snow extends from Northern Ireland southward past Dublin, and from Scotland southward into England. Snow cover stops short of London; the white expanses in that area are clouds. Snow and clouds present an almost uniform white to the satellite sensor, but clouds can be distinguished from the underlying snow by their billowy shapes and indistinct margins.
The United Kingdom Met Office forecast that the cold weather would gradually loosen its grip on the region. For December 9 and 10, 2010, the Met Office forecast rain, but also warned of widespread icy roads.
A huge impact may have formed the Moon, but other large impacts could have determined the makeup of Earth and other planetary bodies. Image Credit: Joe Tucciarone
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One of the fundamental problems in planetary science is trying to determine how planetary bodies in the inner solar system formed and evolved. A new computer model suggests that huge objects – some as big as large Kuiper Belt Objects like Pluto and Eris — likely pummeled the Earth, Moon and Mars during the late stages of planetary formation, bringing heavy metals to the planetary surfaces. This model – created by various researchers from across the NASA Lunar Science Institute — surprisingly addresses many different puzzles across the Solar System, such as how Earth could retain metal-loving, elements like gold and platinum found in its mantle, how the interior of the Moon could actually be wet, and the strange distribution in the sizes of asteroids.
“Most of the evidence of what happened during the late stages of planetary formation has been erased over time,” said Bill Bottke from the Southwest Research Institute, who led the research team. “The trail we’ve been tracking on these worlds is pretty cold and to be able to dig more information out of what we have and be able answer some long standing problems is pretty exciting.”
Bottke told Universe Today that the story this new model tells “is not as complicated as it looks at first glance,” he said. “It includes a lot of concepts together, and some of the concepts have actually been around for awhile.”
Bottke and his team have published their results in the journal Science.
The researchers started with the widely accepted theory of how our Moon was created by a giant impact between the early Earth and another Mars-sized planetary body. “This was the most traumatic event the Earth probably ever went through, and that was the time when presumably the Earth and Moon both formed their cores,” Bottke said.
The heavy iron fell to the center of the two bodies, and so-called highly siderophile, or metal-loving, elements such as rhenium, osmium platinum, palladium, and gold should have followed the iron and other metals to the core in the aftermath of the Moon-forming event, leaving the rocky crusts and mantles of these bodies void of these elements.
“These elements love to follow the metal,” Bottke said, “so if the metal is draining to the core, these elements would want to drain with them. So if this is right, what we would expect that rocks derived from our mantle should have almost no highly siderophile elements, maybe 10 to the minus 5th level or so. But surprisingly, that is not what we see. They are only less abundant by a factor of less than 200, compared to what we would expect, a factor of 100,000 or so.”
Bottke said this problem has been argued about since the 1970’s, with various suggestions on how to answer the problem.
“The most viable answer is that after the Moon forming impact took place, there were also other things that hit the Earth during the late stages of planet formation, objects that were smaller, and these smaller objects replenished these elements and gave us the abundance we see today. This is what we refer to as late accretion,” he said.
On the Moon, the same thing was happening. But there was a problem with this scenario. The ratio of these elements on the Earth compared with rocks on the Moon is about 1000 to 1.
“The gravitational cross section of the Earth is about 20 times that of the Moon,” Bottke said, “So for every object that hit the Moon, about twenty should have hit the Earth. And if late accretion delivered these elements, you should have about a 20 to 1 ratio. But that is not what we see—we see a 1000 to 1 ratio.”
Bottke – a planetary dynamacist — discussed this with colleague David Nesvorny, also from SWRI, as well as geophysical-geochemical modelers, such as Richard Walker from the University of Maryland, James Day from the University of Maryland, and Linda Elkins-Tanton from the Massachusetts Institute of Technology.
They came up with a computer model that seemed to provide an answer.
“By playing roulette with these objects, I found that very often the Earth was getting hit by huge impactors that the Moon would never see,” Bottke said. “This result suggests that the things hitting the Earth and Moon at the end of the planet formation period was dominated by very large objects.”
The model predicted that the largest of the late impactors on Earth, at 2,400 – 3,200 km (1,500-2,000 miles) in diameter, while those for the Moon, at approximately 240 – 320 km.
Bottke called that a “cute” result – but they needed more supporting evidence. So, they took a look at the last surviving population of the things that built the planets, the inner asteroid belt. “You find large asteroids like Ceres, Vesta and Pallas” Bottke said, so there are the large ones at 500 to 900 km, but then your next largest asteroids are only about 250 km. This matched up with the sizes that our model came up with,” in which no asteroids with “in-between” sizes are observed in this region.
Maps of Mars' global topography. Credit: NASA
Next, they looked at Mars, which has some very large impact basins which are probably left over from the days of when the planet formed, including the Borealis Basin, which is so large it likely accounts for the differences in the northern and southern hemispheres on the Red Planet.
“We looked and projected the size of the impactors that would have created those impact basins and we saw the distribution of sizes was very much like what was predicted for the Earth and Moon, and also what is found in the inner asteroid belt.
So all those things together — the theoretical basis, the observational evidence from elements on the Earth and Moon, and impacts on Mars collectively says something about the distribution of sizes of objects towards the end of planetary formation.
And what are the implications?
“We could make predictions for what was hitting the Earth, Moon and Mars at that time, and they line up with what we see on the surfaces,” Bottke said. “On Mars we can play a game of what is the biggest projectiles that should have hit Mars, and it matches up well with the size that big basin that formed on Mars, and also produced the abundances of elements we see there.”
“For the Moon, the biggest impactors would be 250-300 km, which is about the size of the south pole Aiken basin,” Bottke continued. “For the Earth, these big impactors explain why some of these impacts managed to hit the Earth and not all the elements went to the core of the Earth.”
Bottke said that adding to the complications, some of the biggest impacts actually may have plowed through the Earth and actually came out the other side — in a very fragmented state — and rained back down on Earth. “If this is true, this provides a way to spread fragments all the way across the Earth,” he said, “but how the debris gets redistributed around the planetary body is a really interesting question. That part needs a lot more work and is simply at the edge right now of what we can do numerically.”
When it comes to water on the Moon’s interior – which was once thought to be dry, but recent sample measurements, however, suggest that the water content in the lunar mantle is between 200 and several thousand parts per billion — Bottke’s model could also address this issue.
“If true,” the team writes in their paper, “it is possible that the same projectile that delivered most of the Moon’s HSEs may have also have provided it with water….Late accretion provides an alternative explanation in case lunar mantle water cannot migrate from the post–giant impact Earth to a growing Moon through a hot and largely vaporized protolunar disk.”
As to why smaller projectiles hit the Moon as compared to Earth, Bottke said it is just a numbers game. “We start with a population which has a certain number of big things, middle sized things and small things,” he said. “And we randomly choose projectiles from that population and for every one big guy that hits the Moon, 20 hit the Earth. And we play that game, and if the number of projectiles is limited, if the Moon only gets hit once or twice from this population, that means the Earth gets hit 20-30 times, that is enough to give us – on most occasions – what we see.”
Bottke said this research gave him a chance to work with geochemists, “who have all sorts of interesting things to say which help constrain the processes that brought about planet formation. The problem is that sometimes they have great information but they don’t have a dynamical process that can work. So by working together I think we were able to come up with some interesting results.”
“The most exciting thing for me is that we should be able to use these abundances that we have on the Earth, Moon and Mars to really tell the story about planet formation,” Bottke said.
NASA’s Cassini Spacecraft is doing some awesome stuff. Stay tuned to NASA’s twitter feed Space Cadets, today should be interesting. I’m Benjamin Higginbotham and this is your SpacePod for November 30th, 2010. Continue reading “Cassini visits Enceladus – SpacePod 2010.11.30”
Trackable objects in Low Earth Orbit. Image Credit: ESA
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Russia is looking to build a $2 billion orbital “pod” that would sweep up satellite debris from space around the Earth. According to a post on the Russian Federal Space Agency, Roscosmos’ Facebook site, (which seems to confirm an earlier article by the Interfax news agency) the cleaning satellite would work on nuclear power and be operational for about 15 years. The Russian rocket company, Energia proposes that they would complete the cleaning satellite assembly by 2020 and test the device no later than in 2023.
“The corporation promises to clean up the space in 10 years by collecting about 600 defunct satellites on the same geosynchronous orbit and sinking them into the oceans subsequently,” Victor Sinyavsky from the company was quoted as saying.
Sinyavsky said Energia was also in the process of designing a space interceptor that would to destroy dangerous space objects heading towards the Earth.
No word on exactly how the space debris cleaner would work, of how it would push dead satellites and other debris into a decaying orbit so that objects would burn up in the atmosphere, or if it might somehow gather up or “vacuum” debris. But at least someone is thinking about space debris and asteroid deflection and putting more than just a few rubles (60 billion of ’em) towards these concepts.
The Delta IV rocket now scheduled for launch on Nov. 21, 2010. Credit: Alan Walters (awaltersphoto.com) for Universe Today
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Those waiting for a launch from Florida’s Space Coast will have to wait a little more. The liftoff of a United Launch Alliance (ULA) Delta IV Heavy rocket has been pushed back yet again, and is now scheduled for Sunday, Nov. 21 at 5:58 p.m. EST (2258 GMT) from Space Launch Complex 37 (SLC 37) at Cape Canaveral Air Force Station. The rocket will carry a National Reconnaissance Office payload.
Launch Complex 37 at Cape Canaveral Air Force Station. Credit: Alan Walters (awaltersphoto.com) for Universe Today.
Delayed from the 18th, the next countdown started on Friday, but this too was not to be. As technicians started to fuel up the rocket’s twin strap on boosters encountered temperature anomalies. Engineers did not want to give an estimate as to when the rocket will be ready for launch – until they had a chance to unload the fuel and give the vehicle a closer look.
The Delta IV with a NRO payload. Photo Credit: Universe Today/Alan Walters - awaltersphoto.com
The payload for this mission is a classified spy satellite. In media advisories released by the 45th Space Wing it is described only as a ‘Galaxy 3.’ The 45th is stationed out of Patrick Air Force Base. The Delta IV Heavy is the largest rocket in the Delta 4 family, with three booster cores combined to form what is essentially a triple-bodied rocket.
As far as space shuttle Discovery, NASA managers are still keeping all their options open. Inspectors this week found a fourth crack in support beams on the external fuel tanks of the space shuttle. The work to repair the cracks is ongoing, but the teams will need to complete an engineering review and develop the necessary flight rationale in order to launch with a damaged tank. On Thursday, NASA announced that the flight will launch no earlier than Dec. 3, four days after the opening of a short end-of-year launch window.
The window closes Dec. 6. If NASA cannot get Discovery off the ground in the next available launch window, there is only one other planned launch at KSC/CCAFS for this year. This is the Dec. 7 launch of SpaceX’s Falcon-9 with its Dragon spacecraft payload. If this launch happens before the end of this year, it will mark the first demonstration flight of the $1.6 billion Commercial Orbital Transportation Services contract that the private space firm has with the space agency.
The first image from NASA's new geography trivia contest.
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You can now test your knowledge of the world’s geography in a new trivia game on Twitter sponsored by NASA and the astronauts on board the International Space Station. It is kind of like our own “Where In the Universe Challenge” but strictly of images from Earth, and in this contest, there are even actual prizes. Astronaut Scott Kelly started the game this week, which is Geography Awareness Week. His vantage point is perfect for hosting the game, as where else can you get a better view of the various geographical features on our planet than from the International Space Station?
First of all, you have to be on Twitter, and follow Kelly: @StationCDRKelly. He’ll post a link to an image he took, and the first person to correctly identify the place depicted in his photos will win an autographed copy of the picture.
“Expanding our geography knowledge is essential to our economic well-being, our relationships with other nations and the environment,” Kelly said. “It helps us make sense of our world and allows us to make connections between people and places. Space exploration is a global endeavor, and the International Space Station is the result of these connections.”
The new trivia game is a way to engage the public in the activities of the ISS, and the pictures that Kelly, and other astronauts take from the station aren’t all just fun and games. “From the cupola, which is much like a bay window in a house, we are able to take pictures for many scientific reasons, but also to share with the public what we are learning about the planet on which we live,” Kelly said.
Kelly launched to the space station along with two Russian cosmonauts, Alexander Kaleri and Oleg Skripochka on Oct. 8. He is set to return to Earth March 16, 2011. The space station and its six crew members orbit the Earth more than a dozen times each day, traveling more than 320 km (200 miles) above Earth at 28,000 kph (17,500 mph).
A new instrument called the Search for Extra-Terrestrial Genomes (STEG)
is being developed to find evidence of life on other worlds. Credit: NASA/Jenny Mottor
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The idea that a tiny organism could hitchhike aboard a mote of space dust and cross vast stretches of space and time until it landed and took up residence on the early Earth does seem a bit implausible. More likely any such organisms would have been long dead by the time they reached Earth. But… might those long dead alien carcasses still have provided the genomic template that kick started life on Earth? Welcome to necropanspermia.
Panspermia, the theory that life originated somewhere else in the universe and was then transported to Earth requires some consideration of where that somewhere else might be. As far as the solar system is concerned – the most likely candidate site for the spontaneous formation of a water-solvent carbon-based replicator is… well, Earth. And, since all the planets are of a similar age, the only obvious reason to appeal to the notion that life must have spontaneously formed somewhere else, is if a much longer time span than was available in the early solar system is required.
Opinions vary, but Earth may have offered a reasonably stable and watery environment from about 4.3 billion years until 3.8 billion years ago – which is about when the first evidence of life becomes apparent in the fossil record. This represents a good half billion years for some kind of primitive chemical replicator to evolve into a self-contained microorganism capable of metabolic energy production and capable of building another self-contained microorganism.
Half a billion years sounds like a generous amount of time – although with only one example to go by, who knows what a generous amount of time really is. Wesson (below) argues that it is not enough time – referring to other researchers who calculate that random molecular interactions over half a billion years would only produce about 194 bits of information – while a typical virus genome carries 120,000 bits – and an E. coli bacterial genome carries about 6 million bits.
A counter argument to this is that any level of replication in a environment with limited raw materials favors those entities that are most efficient at replication – and continues to do so generation after generation – which means it very quickly ceases to be an environment of random molecular interactions.
Put the term panspermia in a search engineand you get (left) ALH84001, a meteorite from Mars which has some funny looking structures which may just be mineral deposits; and (right) a tardigrade - a totally terrestrial organism that can endure high levels of radiation, desiccation and near vacuum conditions - although it much prefers to live in wet moss. Credit: NASA
The mechanism through which a dead alien genome usefully became the information template for further organic replication on Earth is not described in detail and the case for necropanspermia is not immediately compelling.
The theory still requires that the early Earth was ideally primed and ripe for seeding – with a gently warmed cocktail of organic compounds, shaken-but-not-stirred, beneath a protective atmosphere and a magnetosphere. Under these circumstances, the establishment of a primeval replicator through a fortuitous conjunction of organic compounds remains quite plausible. It is not clear that we need to appeal to the arrival of a dead interstellar virus to kick start the world as we know it.
Merapi Volcano on November 10, 2010, when the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite. Credit: NASA
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For about three weeks, Indonesia’s Mount Merapi has been belching out lava, as well as ash and gas, clouding the atmosphere above. This satellite image, taken by NASA’s MODIS instrument on the Terra satellite, shows the volcano now settling down and is the most cloud-free satellite view of the volcano that we’ve been able to see. Thick ash is still rising and the volcano is still considered to be erupting at dangerous levels. Merapi is one of Indonesia’s most active volcanoes, and this eruption has been the most violent since the 1870’s.
The dark brown streak down the southern face of the volcano is ash and other volcanic material deposited by a pyroclastic flow or lahar. The volcano has been blamed for 156 deaths and about 200,000 people had to evacuate. The ash also caused flights to be delayed or canceled.
See below for a thermal image of the lava flow.
The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA’s Terra satellite captured the thermal signature of hot ash and rock and a glowing lava dome on Mount Merapi on Nov. 1, 2010. Credit: NASA.
As a very active volcano, Merapi poses a constant threat to thousands of people in Indonesia. The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA’s Terra satellite captured the thermal signature of hot ash and rock and a glowing lava dome. The thermal data is overlaid on a three-dimensional map of the volcano to show the approximate location of the flow. The three-dimensional data is from a global topographic model created using ASTER stereo observations.
For more information see NASA’s Earth Observatory website.
At best, the few extrasolar planets we have imaged directly are just points of light. But what can that light tell us about the planet? Maybe more than we thought. As you probably know the, Deep Impact spacecraft flew by comet Hartley 2 today, taking images from only 700 km away. But maneuvering to meet up with the comet is not the only job this spacecraft has been doing. The EPOXI mission also looked for ways to characterize extrasolar planets and the team made a discovery that should help identify distinctive information about extrasolar planets. How did they do it? By using the Deep Impact spacecraft to look at the planets in our very own solar system.
The spacecraft imaged the planetary bodies in our solar system — in particular the Earth, Mars and our Moon — (see here for movies of the Moon transiting Earth) and astronomer Lucy McFadden and UCLA graduate Carolyn Crow compared the reflected red, blue, and green light and grouped the planets according to the similarities they saw. The planets fall into very distinct regions on this plot, where the vertical direction indicates the relative amount of blue light, and the horizontal direction the relative amount of red light.
This suggests that when we do have the technology to gather light from individual exoplanets, astronomers could use color information to identify Earth-like worlds. “Eventually, as telescopes get bigger, there will be the light-gathering power to look at the colors of planets around other stars,” McFadden says. “Their colors will tell us which ones to study in more detail.”
On the plot, the planets cluster into groups based on similarities in the wavelengths of sunlight that their surfaces and atmospheres reflect. The gas giants Jupiter and Saturn huddle in one corner, Uranus and Neptune in a different one. The rocky inner planets Mars, Venus, and Mercury cluster off in their own corner of “color space.”
But Earth really stands out, and its uniqueness comes from two factors. One is the scattering of blue light by the atmosphere, called Rayleigh scattering, after the English scientist who discovered it. The second reason Earth stands out in color is because it does not absorb a lot of infrared light. That’s because our atmosphere is low in infrared-absorbing gases like methane and ammonia, compared to the gas giant planets Jupiter and Saturn.
“It is Earth’s atmosphere that dominates the colors of Earth,” Crow says. “It’s the scattering of light in the ultraviolet and the absence of absorption in the infrared.”
So, this filtering approach could provide a preliminary look at exoplanet surfaces and atmospheres, giving us an inkling of whether the planet is rocky or a gas planet, or what kind of atmosphere it has.
EPOXI is a combination of the names for the two extended mission components for the Deep Impact spacecraft: the first part of the acronym comes from EPOCh, (Extrasolar Planet Observations and Characterization) and the flyby of comet Hartley 2 is called the Deep Impact eXtended Investigation (DIXI).
