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How Was Mars Made? | Formation of Mars

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The planet Mars was formed, along with the rest of the solar system, about 4.6 billion years ago. But exactly how the planets formed remains a subject of debate. Currently, two theories are duking it out for the role of champion.

The first and most widely accepted theory, core accretion, works well with the formation of the terrestrial planets like Mars but has problems with giant planets. The second, the disk instability method, may account for the creation of these giant planets. 

Artist’s conception of our solar system’s solar nebula, the cloud of gas and dust from which the planets formed.

Credit: Painting copyright William K. Hartmann, Planetary Science Institute, Tucson

Scientists are continuing to study planets in and out of the solar system in an effort to better understand which of these methods is most accurate. 

The leading theory, known as core accretion, is that the solar system began as a large, lumpy cloud of cold gas and dust, called the solar nebula. The nebula collapsed because of its own gravity and flattened into a spinning disk. Matter was drawn to the center of the disk, forming the sun.  

Other particles of matter stuck together to form clumps called planetesimals. Some of these combined to form asteroids, comets, moons and planets. The solar wind — charged particles streaming out from the sun — swept away the lighter elements, such as hydrogen and helium, leaving behind mostly small, rocky worlds. In the outer regions, however, gas giants made up of mostly hydrogen and helium formed because the solar wind was weaker.

Exoplanet observations seem to confirm core accretion as the dominant formation process. Stars with more “metals” — a term astronomers use for elements other than hydrogen and helium — in their cores have more giant planets than their metal-poor cousins. According to NASA, core accretion suggests that small, rocky worlds should be more common than the more massive gas giants.

The 2005 discovery of a giant planet with a massive core orbiting the sun-like star HD 149026 is an example of an exoplanet that helped strengthen the case for core accretion.

“This is a confirmation of the core accretion theory for planet formation and evidence that planets of this kind should exist in abundance,” said Greg Henry in a press release. Henry, an astronomer at Tennessee State University, Nashville, detected the dimming of the star.

In 2018, the European Space Agency plans to launch the CHaracterising ExOPlanet Satellite (CHEOPS), which will study exoplanets ranging in sizes from super-Earths to Neptune. Studying these distant worlds may help determine how planets in the solar system formed.

“In the core accretion scenario, the core of a planet must reach a critical mass before it is able to accrete gas in a runaway fashion,” said the CHEOPS team

“This critical mass depends upon many physical variables, among the most important of which is the rate of planetesimals accretion.”

By studying how growing planets accrete material, CHEOPS will provide insight into how worlds grow.

Core accretion was first postulated in the late 18th century by Immanuel Kant and Pierre Laplace. Nebula theory helps explain how the planets in our solar system were formed. But with the discovery of “Super-Earth” planets orbiting other stars, a new theory, known as disk instability was proposed. 

Although the core accretion model works fine for terrestrial planets, gas giants would have needed to evolve rapidly to grab hold of the significant mass of lighter gases they contain. But simulations have not been able to account for this rapid formation. According to models, the process takes several million years, longer than the light gases were available in the early solar system. At the same time, the core accretion model faces a migration issue, as the baby planets are likely to spiral into the sun in a short amount of time.

According to a relatively new theory, disk instability, clumps of dust and gas are bound together early in the life of the solar system. Over time, these clumps slowly compact into a giant planet. These planets can form faster than their core accretion rivals, sometimes in as little as a thousand years, allowing them to trap the rapidly-vanishing lighter gases. They also quickly reach an orbit-stabilizing mass that keeps them from death-marching into the sun.

According to exoplanetary astronomer Paul Wilson, if disk instability dominates the formation of planets, it should produce a wide number of worlds at large orders. The four giant planets orbiting at significant distances around the star HD 9799 provides observational evidence for disk instability. Fomalhaut b, an exoplanet with a 2,000-year orbit around its star, could also be an example of a world formed through disk instability, though the planet could also have been ejected due to interactions with its neighbors.

The biggest challenge to core accretion is time — building massive gas giants fast enough to grab the lighter components of their atmosphere. Recent research on how smaller, pebble-sized objects fused together to build giant planets up to 1000 times faster than earlier studies.

“This is the first model that we know about that you start out with a pretty simple structure for the solar nebula from which planets form, and end up with the giant-planet system that we see,” study lead author Harold Levison, an astronomer at the Southwest Research Institute (SwRI) in Colorado, told Space.com in 2015.

In 2012, researchers Michiel Lambrechts and Anders Johansen from Lund University in Sweden proposed that tiny pebbles, once written off, held the key to rapidly building giant planets.

“They showed that the leftover pebbles from this formation process, which previously were thought to be unimportant, could actually be a huge solution to the planet-forming problem,” Levison said.

Levison and his team built on that research to model more precisely how the tiny pebbles could form planets seen in the galaxy today. While previous simulations, both large and medium-sized objects consumed their pebble-sized cousins at a relatively constant rate, Levison’s simulations suggest that the larger objects acted more like bullies, snatching away pebbles from the mid-sized masses to grow at a far faster rate.

“The larger objects now tend to scatter the smaller ones more than the smaller ones scatter them back, so the smaller ones end up getting scattered out of the pebble disk,” study co-author Katherine Kretke, also from SwRI, told Space.com. “The bigger guy basically bullies the smaller one so they can eat all the pebbles themselves, and they can continue to grow up to form the cores of the giant planets.”

In 2018, NASA will launch the InSight mission to Mars that will study the planet’s interior.

“But InSight is more than a Mars mission — it is a terrestrial planet explorer that will address one of the most fundamental issues of planetary and solar system science — understanding the processes that shaped the rocky planets of the inner solar system (including Earth) more than four billion years ago,” according to NASA.

“InSight seeks to answer one of science’s most fundamental questions: How did the terrestrial planets form?”

Whether Mars got its start through disk instability or core or pebble accretion, it continued to pack on the weight as it grew. Models suggest that the Red Planet should be about as large as Venus and Earth if gas and dust were smoothly spread through the solar system. Instead, Mars is only 10 percent as massive, suggesting that it formed in a region low on planetary building blocks.

Enter the Grand Tack model, the leading theory to explain the so-called “small Mars problem.” According to the model, Jupiter and Saturn migrated toward the sun shortly after their birth before tacking like a sailboat and returning to the outer solar system. Along the way, they would have swept up much of the debris that should have fed Mars’ formation.

The western scarp of Olympus Mons has both steep and gentle slopes with clear channels, some likely created by flowing liquid, perhaps water, and some apparently carved by glaciers.

The western scarp of Olympus Mons has both steep and gentle slopes with clear channels, some likely created by flowing liquid, perhaps water, and some apparently carved by glaciers.

Credit: Nature/ESA/G. Neukum

“Provided that Jupiter changed direction close to 1.5 AU, the growth of Mars would be successfully stunted while leaving enough material closer to the sun to form Earth and Venus,” John Chambers of the Carnegie Institution for Science wrote in a 2014 “Perspectives” piece published in the journal Nature.

Another possibility is that regions of low density formed naturally in the protoplanetary disk. 

“If this partial gap survived long enough, it could have been preserved in the distribution of planetesimals and planetary embryos that formed subsequently,” Chambers writes. “The simulations performed by Izidoro show that reducing the number of planetary building blocks near Mars’ current orbit by 50 to 75 percent favors the formation of a puny Red Planet.”

Another option is that Mars actually got its start in the asteroid belt, then migrated toward the sun because of its interaction with planetesimals.

“Since Mars is more massive than the planetesimals, it tends to lose energy when it scatters these planetesimals because it passes them to Jupiter, which then ejects them from the solar system,” Ramon Brasser, lead author and associate professor at the Tokyo Institute of Technology’s Earth-Life Science Institute, told Space.com.

Like all planets, Mars became hot as it formed because of the energy from these collisions. The planet’s interior melted and denser elements such as iron sank to the center, forming the core. Lighter silicates formed the mantle, and the least-dense silicates formed the crust. Mars probably had a magnetic field for a few hundred million years, but as the planet cooled, the field died. 

The young Mars had active volcanoes, which spewed lava across its surface, and water and carbon dioxide into the atmosphere. But there is no tectonic activity on Mars, so the volcanoes remained stationary and grew with each new eruption.

The volcanic activity also probably gave Mars a thicker atmosphere. Mars’ magnetic field protected the planet from radiation and solar wind. With a higher atmospheric pressure, water probably flowed on Mars’ surface, studies indicate. But about 3.5 billion years ago, Mars began to cool. Volcanoes erupted less and less and the magnetic field disappeared. The unprotected atmosphere was blown away by solar wind and the surface was bombarded by radiation.

Under these conditions, liquid water cannot exist on the surface. Studies suggest water is be trapped underground in both liquid and frozen forms and in the ice sheets of the polar ice caps.

All life as we know it requires liquid water, so there is much interest in finding evidence of it on Mars.

— Additional reporting by Nola Taylor Redd, Space.com Contributor

Space.com is the premier source of space exploration, innovation and astronomy news, chronicling (and celebrating) humanity's ongoing expansion across the final frontier. We transport our visitors across the solar system and beyond through accessible, comprehensive coverage of the latest news and discoveries. For us, exploring space is as much about the journey as it is the destination. So from skywatching guides and stunning photos of the night sky to rocket launches and breaking news of robotic probes visiting other planets, at Space.com you’ll find something amazing every day.

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Astronomical Odds: Becoming an Astrophysicist Keeps Getting Tougher

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The dazzling star TYC 3203-450-1, in the constellation Lacerta, shines much closer to Earth than the distant galaxy NGC 7250, also visible in this Hubble Space Telescope image.

Paul Sutter is an astrophysicist at The Ohio State University and the chief scientist at COSI science center. Sutter is also host of “Ask a Spaceman” and “Space Radio,” and leads AstroTours around the world. Sutter contributed this article to Space.com’s Expert Voices: Op-Ed & Insights.

Ah, the life of an astrophysicist. The money. The parties. The paparazzi. No wonder so many young people flock to their nearest large research universities with stars in their eyes and dreams of Nobels in their hearts, buoyed by fantasies of solving the mystery of dark energy or cracking the enigma of quantum gravity. 

It’s true, sitting at the forefront of academic research is a unique, and sometimes thrilling, position. You are pushing the boundaries of human knowledge, and every experimental result, theoretical insight or recorded observation brings us closer to working out nature’s secrets. And for a moment, scientific discovery is a very private experience. Until you share your results with your colleagues in the community and the public in the wider world, you are the only human on the planet to know that fact, that insight, that datum. [8 Baffling Astronomy Mysteries]

And once you release that information, the volume of humanity’s understanding grows, most times by just a little, but sometimes by quite a lot. And at the end of your career, whether you end your journey as a young, freshly minted Ph.D. setting out into industry or a weathered and wizened emeritus professor, you can rest easy, knowing that academics and non-academics around the world are better off for your work.

Except, there are no jobs. At least, there are very few open faculty or research-lab positions for the people who want them (i.e., young Ph.D. holders). This isn’t new; academic jobs have always been on the rare side. But with the growth of university populations in the past decades, there is a glut of bachelors from all majors, including astronomy and physics. For example, there were roughly twice as many physics bachelor degrees awarded in 2015 than in 1995. And the increased undergraduate population has opened up funds for departments to host more graduate students, who do the majority of the teaching assistantship work. 

So, there are more Ph.D. grads created than ever before, but the same amount of — or fewer — long-term research jobs. Adding to the mix is the postdoctoral research position (often abbreviated as “postdoc”), a temporary job lasting two to five years in which you work to prove yourself as an independent researcher worthy of a faculty position.

The concept of a postdoc isn’t a bad one: How far can you fly without your advisor as the wind beneath your wings? A postdoc also gives you some experience working with a different group other than your graduate institution, so the interconnected web of worldwide researchers grows more tightly knit.

You would think that with a lot of Ph.D. holders and not a lot of long-term jobs, there wouldn’t be a lot of short-term postdoc positions. And that used to be the case; it was generally very tough and very competitive to get a postdoc, but if you did, you would most likely end up in a faculty position somewhere.

But in recent decades, with physical science research funding generally stalling or falling, it’s easier for a department, lab, or center to make a case for a term-limited grant with a small set of objectives than ask for the big bucks necessary for a lifetime, open-ended faculty position. The result: more postdoc positions. So now the field is in a state where about half the newly-minted Ph.D.’s slide right into a postdoc position.

Which is good! If you’re really into short-term positions. But now there are still a lot of faculty-wannabes in the system, and still not enough positions for them. There’s money for continued postdoc positions, creating a dangerous trend: Instead of the old “Ph.D. -> small chance of a postdoc -> faculty” pipeline, we have a “Ph.D. -> postdoc -> second postdoc -> maybe another postdoc -> small chance of a faculty job” system.

The result is the same: Most people with a Ph.D. in physics or astronomy won’t end up in a job in that field. This isn’t necessarily a bad thing, except that the harsh cutoff no longer comes when you’re a fresh-faced, probably single 20-something, able to easily and nimbly pivot to another career. Now, the people getting nudged out of the system are in their 30s, haven’t had a stable job for a decade, might be married, might want to start raising a family, and are generally making far less money than peers in their age and skill group.

And if you do get a faculty position, it’s another five years before your tenure review finally cements your career. Some unscrupulous universities even intentionally hire two junior faculty on a track for the same long-term professorship, taking a “two scientists enter, one scientist leaves” approach to fostering top talent.

For a graduate student or postdoc, this career path is not that rewarding. You get built up assuming you’re training for a career in academia, get a degree, then continue to be shunted from position to position. You get to do what you love, true, but with a clock always ticking in the background, reminding you that your time at the scientific forefront is probably nearing an end.

If that’s the system we have, then that’s the system we have, whether I think it’s fair or not. Some people think that a brief time as an active researcher is enough, and more power to them. And a bachelor’s or Ph.D. in physics or astronomy is a major asset for many kinds of jobs in industry, from finance to writing to consulting to Silicon Valley. Many science trainees are able to smoothly transition to a new life, making rewarding (both financially and mentally) lives for themselves. They also tend to make more money, which is nice.

Promising young students are more than welcome to take a chance at the academic wheel of fortune — assuming they know how the game is played. But we’re doing a very bad job at educating undergraduate and graduate students about the prospects of an academic career and what they might have to sacrifice (stability, money, relationships) in order to attain a professorship, and what other noble (rather than Nobel) options might await them with their degrees.

If we want the astrophysics community to thrive and attract new generations of scientists with new insights and new abilities — and especially if we want to encourage youngsters to explore STEM careers — then we first have to be honest about the state of our field.

Learn more by listening to the episode “Why can’t I be an astrophysicist?” on the “Ask a Spaceman” podcast, available on iTunes and on the web at http://www.askaspaceman.com. Thanks to @92Rufino and Vicki K. for the questions that led to this piece! Ask your own question on Twitter using #AskASpaceman or by following Paul @PaulMattSutter and facebook.com/PaulMattSutter.

Follow us @Spacedotcom, Facebook and Google+. Original article on Space.com

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Enormous 'El Gordo' Galaxy Cluster Captured in Hubble Image

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The enormous “El Gordo” galaxy cluster, officially called ACT-CLJ0102-4915, has the mass of 3 million billion suns.

An incredible photo from the Hubble Space Telescope showcases an enormous galaxy cluster that weighs in at a whopping 3 million billion suns.

Due to its massive size, the galaxy cluster has been nicknamed “El Gordo” (Spanish for “the fat one”). Research suggests the cluster is the largest, hottest and brightest X-ray galaxy cluster ever discovered in the distant universe, NASA officials said in a statement

Galaxy clusters, groups of galaxies held together by gravity, are the biggest objects in the distant universe. These clusters take billions of years to form, as smaller groups of galaxies slowly move closer to each other, NASA officials said in the statement. 

The El Gordo galaxy cluster — officially known as ACT-CL J0102-4915 — is located more than 7 billion light-years from Earth. The cluster was first discovered in 2012 by a trio of telescopes, the European Southern Observatory’s Very Large Telescope, NASA’s Chandra X-ray Observatory and the Atacama Cosmology Telescope in Chile. These observations showed that El Gordo is actually the product of two galaxy clusters, which are in the process of colliding at a speed of millions of kilometers per hour, according to the statement. 

Dark matter and dark energy are believed to heavily influence the formation and evolution of galaxy clusters. Therefore, studying these clusters can help astronomers learn more about the elusive phenomenon, NASA officials said in the statement.

In fact, observations made by Hubble in 2014 showed that most of El Gordo’s mass is concealed in the form of dark matter, according to the statement. 

“Evidence suggests that El Gordo’s ‘normal’ matter — largely composed of hot gas that is bright in the X-ray wavelength domain — is being torn from the dark matter in the collision,” NASA officials said in the statement. “The hot gas is slowing down, while the dark matter is not.” 

The recent image, released by NASA on Jan. 16, was captured using Hubble’s Advanced Camera for Surveys and Wide-Field Camera 3. El Gordo is one of 41 giant galaxy clusters surveyed as part of the Reionization Lensing Cluster Survey (RELICS), which is a joint observing program led by the Hubble and Spitzer space telescopes, according to the NASA statement.

RELICS is designed to search for the brightest distant galaxies in the universe. This data will be used to identify faraway clusters of interest for further study by the James Webb Space Telescope, which is scheduled to launch sometime in the spring of 2019. 

Follow Samantha Mathewson @Sam_Ashley13. Follow us @Spacedotcom, Facebook and Google+. Original article on Space.com.

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New National Defense Strategy to Shed Light on Pentagon's Thinking About War in Space

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Defense Secretary Jim Mattis at U.S. Northern Command headquarters in Colorado Springs, Colorado.

WASHINGTON — Space and cyber warfare moved up the national security priority list during the Obama administration, and are expected to rank even higher under the Trump presidency.

Details on how the military views outer space and cyberspace as battlefronts in future wars should emerge in the national defense strategy that Defense Secretary Jim Mattis is expected to unveil Friday.

The national defense strategy — a forward-looking take on the challenges facing the U.S. military and how it is posturing itself to tackle those threats — is what used to be known as the QDR, or Quadrennial Defense Review. Congress last year determined that the QDR had no real value and asked the Pentagon to provide instead a more candid picture of its global commitments and requirements. The thinking is that lawmakers need to better understand what resources are needed for the military to fulfill those responsibilities. [The Most Powerful Space Weapons Concepts]

Andrew Philip Hunter, director of the Defense-Industrial Initiatives Group at the Center for Strategic and International Studies, said space and cyber are likely to feature prominently in Secretary Mattis’ first national defense strategy.

In the first year of the Trump administration, space, cyber and missile defense have “really risen on the scope as modernization priorities,” Hunter said Wednesday at a CSIS news conference. Although it is still not clear that the rhetoric about the importance of space and cyber will be matched by policy and funding.

The next Pentagon’s budget could be a show-me moment.

Space and cyber are “new investment categories that are trying to displace, to some extent, existing force structure,” he said. Defense leaders and strategists have said the military needs to invest in modern technology to improve data analysis, intelligence, surveillance and other information-centric capabilities. But most of the Pentagon’s budget today is spent on old-school weapons. This creates a dilemma for the administration as it tries to position the military to win in the so-called “great power competition” against Russia and China.

“In order to dramatically increase investment in space, the Air Force will probably be required to reduce the size of its tactical fighter fleet in order to be able to afford that kind of investment,” Hunter said. “All of the services are being forced to reallocate force structure into the cyber mission in a pretty major way. That’s hard to do.”

Shifting resources away from traditional military systems to emerging areas of warfare like space and cyber will require some heavy political muscle, Hunter said. “That means it has to come from the secretary,” he added. “Left to their own devices, it’s very hard for the services to make that tradeoff. And that’s why, if it’s not articulated in the strategy, if it’s not coming from the secretary, it’s probably not going to happen.”

The new strategy also may begin to answer questions that the space and arms-control communities have been asking for a long time, such as how the military plans to deter attacks as space becomes more militarized,

That is the “big, burning issue that has not been resolved,” said Todd Harrison, director of the Aerospace Security Project and senior fellow at CSIS.

“What are we going to do in space to reestablish or improve a stable deterrent posture?” Harrison asked. “We do not want to fight a war in space. That’s a war that’s not going to go well for anyone,” he insisted. “If you know anything about orbital mechanics and orbital debris, we don’t want it to go there.” Military leaders have made this point as well.

How the Pentagon would deter future enemies from launching attacks in space in unclear, said Harrison. “And we’re at a point now where deterrence is not as clear that it will work in space,” he said. “We’re worried about that. The Department of Defense is worried about that.” He wonders whether this strategy will help reestablish a stable “deterrence posture” in space.

In a leaked draft copy of the soon-to-be-released Nuclear Posture Review, the administration highlights the risks that, if a nuclear crisis erupted, U.S. adversaries would immediately target key strategic space assets such as missile-warning and command-and-control satellites.

“In the nuclear realm, it’s long been understood that if you’re actually getting into a nuclear conflict, that of course both sides are going to try to take out the space assets of the other,” Harrison said. “If you’re at that point, the gloves are off.”

That concern is not new, he noted. But deterrence in space has become more challenging for the United States because the same satellites are used for strategic and tactical missions. Classified communications and intelligence gathering satellites that were created to support a nuclear war routinely are employed in conventional missions.

What the Trump administration has to address, Harrison said, is “how do we architect these systems to do what we need them to do in a nuclear crisis, but also to be resilient to attack in a nonnuclear crisis?”

During the Cold War, only the Soviets posed a credible threat to U.S. space systems. “And we basically had an understanding between the two countries: ‘If you attack our space systems, we’re going to regard that as a prelude of a full-scale nuclear war.” The world today is different, and the U.S. military has become hugely dependent on space, even for low-intensity counterinsurgency operations.

“So why wouldn’t an adversary, even a non-state actor, try to disrupt these systems?” Harrison asked. “And we’ve seen evidence of that, things like jamming our satellite-communications signals in Iraq and Afghanistan,” he said. “It is a much more complicated deterrence problem that we have today. We can’t simply assume that the threat of nuclear retaliation is going to deter someone from interfering with our space systems.”

Deterrence is even more difficult as anonymous cyber attacks can disrupt satellites signals. “You can’t prove it,” said Harrison. “There’s not something blowing up. It’s photons interfering with one another,” he said. “Can we really deter those types of attacks anymore?” And when deterrence fails, “we need architectures in space that can withstand attacks, that are resilient.” Further, “we need a posture that makes us more credible that we can deter these types of actions.”

This story was provided by SpaceNews, dedicated to covering all aspects of the space industry.

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US Air Force's New Missile-Warning Satellite Launching Tonight: Watch It Live

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A United Launch Alliance Atlas V rocket carrying the new SBIRS GEO Fight 4 missile- warning satellite stands atop Space Launch Complex 41 at Cape Canaveral Air Force Station in Florida ahead of a scheduled Jan. 18, 2018, launch.

The U.S. Air Force’s newest early-warning satellite for missile defense will launch into space from Florida tonight (Jan. 18), and you can watch the action live online.

A United Launch Alliance Atlas V rocket will launch the new military satellite, called the Space Based Infrared System (SBIRS) GEO Flight 4, from Space Launch Complex 41 at the Cape Canaveral Air Force Station. Liftoff is scheduled for 7:52 p.m. EST (0052 GMT on Jan. 19).

ULA will provide a live launch webcast beginning at 7:32 p.m. EST (0032 GMT). You can watch it live on Space.com here, or directly from ULA’s YouTube channel.

Built by Lockheed Martin, SBIRS GEO Flight 4 is the fourth member of a growing constellation of early-warning satellites designed to detect the launch of ballistic missiles from space. The satellites fly in geostationary orbits, and carry powerful scanning and infrared surveillance gear to track missile launches from orbit. 

The first two satellites, SBIRS GEO Flights 1 and 2, have been operational since 2013. SBIRS GEO Flight 3 launched in January 2017. Two other satellites, SBIRS GEO Flights 5 and 6, are expected to follow.

The Space Based Infrared System GEO Flight 4 missile-warning satellite is seen during assembly and test at Lockheed Martin’s satellite manufacturing facility in Sunnyvale, California.

Credit: Lockheed Martin

“SBIRS provides our military with timely, reliable and accurate missile warning and infrared surveillance information,” Tom McCormick, vice president of Lockheed Martin’s Overhead Persistent Infrared systems mission area, said in a Nov. 28 statement when SBIRS GEO Flight 4 was shipped to its Florida launch site. “We look forward to adding GEO Flight 4’s capabilities to the first line of defense in our nation’s missile defense strategy.”

Email Tariq Malik at tmalik@space.com or follow him @tariqjmalik and Google+. Follow us @Spacedotcom, Facebook and Google+. Original article on Space.com.

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