Extinction alert: saving the world from a deadly asteroid impact

Michael Dello-Iacovo, UNSW Australia

Sixty-five million years ago, disaster struck the Earth. An asteroid or comet around 10km in diameter slammed into what is now the Yucatan Peninsula in Mexico.

While the idea was ridiculed at first, this event is now widely believed to be the reason the dinosaurs became extinct.

This realisation led to a rallying of scientists and engineers around the world to detect and monitor the asteroids in the heavens, and if need be, to be prepared to deflect one from hitting us.

Today, we have a Planetary Defense Coordination Office under NASA whose sole mission is to prepare us for this unlikely but devastating possibility.

It is believed that we have found all of the asteroids the size of that which killed the dinosaurs (at least those near Earth).

Recent impacts

But there are many smaller asteroids that can still do a lot of damage which are undetected. In 1908, the Tunguska event flattened about 2,000 square kilometres of forest in Siberia.

This asteroid was only about 50 metres across, but we have only found about 1% of the near Earth objects (NEOs) of this size.

Despite being so rare, if a large asteroid did hit Earth, it would cause extraordinary damage. In fact, you’re more likely to be killed by an asteroid than die in a shark attack.

We know about a number of recent asteroid impacts, but we’re still discovering more in the geological record. Currently it’s estimated that NEOs which can cause global ecological effects occur around once every 500,000 years.

Right now, despite being able to detect and track large asteroids (you can look at current known asteroid positions yourself using online databases), we know very little about their interior.

Much of what we do know is based on meteorite samples which have fallen to Earth. But it is difficult to extrapolate small samples to understanding what asteroids look like as a whole.

Asteroid types

Asteroids have several types based on mineral composition, but their internal structure can also potentially take several forms.

Some might be rubble piles, weakly held together by gravity and electrostatic forces, while others might be solid bodies of rock. Different structural types would require different methods of deflection.

For example, a rubble pile might break up if we hit it with an object, with each smaller piece still posing a threat. This might dictate a more finessed approach, such as hitting it with a smart cloud of smaller particles released by a space craft.

The use of explosive devices to move an asteroid is expected to be about 100 times less efficient on porous asteroids compared to more solid bodies.

Inside an asteroid

My research involves repurposing geophysical techniques used for more than a century on Earth to determine the strength and structure of asteroids. To test whether these techniques will work requires simulating asteroid conditions in a lab.

This means we have to recreate the gravity, atmospheric and temperature conditions. We also have to find a material that matches the properties of an asteroid surface to test our equipment on.

NASA performs experiments in low gravity using a parabolic jet, which is temporarily in free fall. Atmospheric conditions can be modified in a vacuum chamber.

Researchers have developed simulant materials that are similar in chemical composition to various classes of asteroids. As well as being useful for testing mining equipment that might be used on asteroids, they can also be used to test geophysical equipment might be able to determine useful properties, such as structure.

Once this technology is proven, it can potentially be used to land on an asteroid and peer into its interior. By understanding its structure, porosity and strength, we can then start to plan deflection strategies for individual asteroids, and for asteroids in general.

Being prepared

The dinosaurs went extinct because they didn’t have a space program. Luckily, we are more prepared (although Australia is still one of just two OECD nations without a space program, the other is Iceland).

If we were to detect an inbound asteroid with warning of at least several years, we can send a mission to find out what it’s made of. Then we can plan the optimal strategy complete with backup plans.

In 1995, a workshop with ex-Cold War US and Russian weapons designers was held to propose a way of deflecting an asteroid if it was detected at the last minute. They came up with (though never built) a nuclear weapon capable of instantly vaporising a 1km asteroid.

It would also have the potential to move an extinction class asteroid out of our path given at least a few months notice, or a comet given two years notice. Given any less time, we may have to be content with evacuating as many people as possible from the predicted landing site.

Asteroid impacts aren’t the only event that might wipe us out. Nuclear warfare, biological terrorism and artificial intelligence all have the potential to destroy us. Some researchers have even suggested that the probability of humanity surviving until 2100 is just one in two.

Given this level of risk, one thing is certain: we can and should spend more time and resources trying to reduce these risks.

Michael Dello-Iacovo, PhD candidate (Mining Engineering), UNSW Australia

This article was originally published on The Conversation. (Reblogged by permission). Read the original article.

 

Picture of Pluto further refined by months of New Horizons data

Mike Summers, George Mason University

When the New Horizons spacecraft made its flyby of Pluto on July 14, 2015, there was worldwide celebration that we’d finally gotten our first detailed look at this completely new type of planet in the outer reaches of our solar system.

But for those of us on the New Horizons science team, that day and those first images were only the beginning. Since then, I’ve been watching with amazement as the New Horizons spacecraft has transmitted spectacular images back that reveal surprises all over the place. We’ve been making discovery after discovery about the dwarf ice planet Pluto and its moon Charon, and this is likely to continue as we get more data back from the spacecraft. Here’s a summary of just a few of our scientific results to date.

What do we see on Pluto’s surface?

Perhaps one of the biggest surprises that was obvious from the very first images was that Pluto has a surface that is incredibly diverse.

Some surface areas, such as those that are heavily cratered from asteroid impacts, seem to date back to just after Pluto formed, about 4.5 billion years ago. Other regions show evidence of geological activity that may have lasted throughout Pluto’s billions of years of history. Enormous ice volcanoes (cryovolcanoes) must have taken a large fraction of Pluto’s history to form. These volcanoes are driven by warm underground liquids, such as, perhaps, water and ammonia, instead of liquid rock-magma that we have on Earth, and their rough, crusty surface is made of stuff that has erupted from deep within Pluto’s interior.

Pluto’s Sputnik Planum captured hearts here on Earth.
NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute, CC BY

Other areas, such as the informally named Sputnik Planum – the heart-shaped, Texas-sized nitrogen ice glacier – show no evidence of asteroid impacts at all, suggesting continual surface activity, such as convection of ices from underground. This surface can’t be more than 10 million years old – a blink of the eye on a geological time scale!

Pluto is geologically active! I doubt there’s a single person on Earth who would have expected to see that!

What’s Pluto made of?

The diverse chemical compositions we’ve seen on Pluto are giving us some important clues to understanding Pluto’s geological history and climate.

Pluto’s rugged, icy cratered plains.
NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute, CC BY

The high-resolution images from the New Horizons cameras show diverse ice reservoirs across Pluto’s surface. By studying the reflected spectra from the surface, we’ve identified several different types of ices: in particular, nitrogen, methane and carbon monoxide. The locations and characteristics of these ice reservoirs mean that there have been long epochs of ice transport across the dwarf planet’s surface.

A darker veneer on top of the ices is probably tholin material – organic compounds processed by solar radiation. These are produced slowly in Pluto’s atmosphere and gently rain down, even now, onto the surface. An enormous darker region, informally named Cthulhu Regio, has a meters-thick layer of this organic tholin material that has built up over billions of years. Frozen water is one of the strongest solids at the low temperatures we see on Pluto. We believe that the ice mountains that extend several miles above the surface are made of water ice – the biggest ice cubes in the solar system.

Charon, too, had some major surprises in store for us. Pluto’s largest moon has an extended equatorial region of smooth plains that may also be due to material that erupted from Charon’s interior via ice volcanoes that then flowed over its surface about four billion years ago. We suspect that was when Charon’s subsurface water ocean froze, causing global fractures as the moon expanded in size (water expands when it freezes).

Charon has dark poles that may be related to volatile gases that escaped from Pluto’s atmosphere only to be captured by the moon’s cold poles. These gases trigger chemical reactions on the surface that, we believe, produce the darker color of the poles.

How does Pluto’s atmosphere work?

The spacecraft’s Alice instrument made observations of sunlight passing through Pluto’s atmosphere. We see absorption features that indicate an atmosphere made up of nitrogen (like Earth’s) with methane, acetylene and ethylene as minor constituents.

Pluto’s small size and low gravity cause it to hold onto its atmosphere much more weakly than larger planets like the Earth (which has 16 times stronger gravity than Pluto). Prior to the New Horizons’ encounter, we expected this would produce an atmosphere that was greatly extended and rapidly escaping to space. But it turned out the upper atmosphere is much colder than we thought it would be and so more compact – the atmosphere does not extend nearly as far into space as we expected and the escape rate of atmospheric gases is extremely slow. But why the atmosphere is so cold is still a complete mystery.

Pluto’s haze is a photochemical smog.
NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute, CC BY

As an atmospheric scientist, I found the most amazing discovery to be the brilliant, light blue, globally extensive haze that we can see because large numbers of small atmospheric particles scatter sunlight. This haze extends hundreds of kilometers into space, and embedded within it are over 20 very thin, but far brighter, layers. We suspect the thin layers are produced by some type of atmospheric wave that causes localized regions of condensation of some as-yet-unknown gas. The largest moon of Saturn, Titan, shows similar layering of haze in its upper atmosphere. So there may be some interesting comparative planetary studies that come out of the analysis of the Pluto data.

Where did Pluto’s moons come from?

The origin of Pluto’s five moons has been a long-standing question. But the flyby observations have given us some critical data that we needed in order to develop convincing explanations.

We believe that Charon is just about as old as Pluto, having formed when Pluto was very young. An impact between Pluto and another large Kuiper Belt object early in their history ejected an enormous amount of debris into orbit around Pluto. As time went on, this orbital debris coalesced into Charon.

Previous speculation was that the four smaller moons are actually asteroids captured by Pluto’s gravity as they passed too near the dwarf planet. But the New Horizons observations showed that these four moons have an unusually high reflectivity – much different than the extremely dark materials that we see on asteroids in the outer solar system. This has led to a compelling argument that the smaller moons are also made of debris from the same impact that formed Charon.

Pluto’s atmosphere is buffeted by protons and electrons streaming from the sun as the solar wind.
H.A. Weaver et al. / Science (2016), Author provided

How does Pluto interact with its space environment?

As the New Horizons spacecraft approached Pluto, there was some concern that a small amount of debris might still remain in orbit around the dwarf planet. A collision between New Horizons and even one particle of debris the size of a grain of sand could cause considerable damage to, or possibly destroy, the spacecraft.

The Student Dust Counter is one part of the science payload New Horizons’ been carrying for a decade.
NASA/New Horizons, CC BY

But the student-built Dust Counter, which measures small micrometer size dust particles in space, detected only a single particle during the flyby – and it was much too small to cause spacecraft damage. This means Pluto’s environment is now largely devoid of debris – all of it likely swept up by the moons early in the system’s history.

The New Horizons spacecraft also carried instruments to study what happens to the solar wind when it encounters Pluto’s atmosphere. The detailed way in which solar wind particles from the sun interact with a planet’s atmosphere provides important clues about the nature of that atmosphere, particularly how far it extends into space and the escape rate of atmospheric gases. The interaction region between Pluto and the solar wind was observed to be much smaller than expected, only about 12 Pluto diameters across. This means that the atmosphere is smaller than expected, and so these results confirm the Alice observations that the upper atmosphere is much colder than expected.

So much more yet to come

These are just a few of the many exciting, and unexpected, results from the New Horizons flyby of Pluto and Charon. The discoveries we’ve already made will mean that textbooks on planetary science must be rewritten. And yet this sampling of the New Horizons results is just from the tip of an ice mountain of data that we’ll be analyzing and writing papers about for many years, perhaps decades. The data are so rich in things we’ve never seen before that I’m sure there are many more surprises yet to come.

Mike Summers, Professor of Planetary Science and Astronomy, George Mason University

This article was originally published on The Conversation. (Reblogged by permission). Read the original article.

 

Discovery of carbon on Mercury reveals the planet’s dark past

Ivy Shih, The Conversation

Mercury has been found to have a dark side with graphite, a crystalline form of carbon commonly found in pencils, being the source of the mysterious dark colouration of the planet’s surface.

The study, published this week in Nature Geoscience, was led by a team from the Johns Hopkins University Applied Physics Laboratory in the US, which analysed measurements collected by NASA’s Messenger spacecraft as it went through its final orbits of Mercury.

The findings not only test theories of early planetary formation but may offer an explanation of the amount of carbon here on Earth.

Remains of a primordial crust

The surface colour of planetary bodies is often an indicator of the elements that make them up. For example, the distinctive rusty red appearance of Mars can be attributed to iron oxide.

It had previously been believed that the iron and titanium were typically responsible for the dark coloration on planetary surfaces. However, Mercury is quite dark, but lacked high enough concentrations of those elements to account for its colour.

“Mercury’s surface was significantly darker than we could account for on the basis of our understanding of Mercury’s surface chemistry,” said Dr Patrick Peplowski, from the Johns Hopkins University Applied Physics Laboratory, and lead author on the study.

“So what was causing Mercury to be so dark?”

By carefully examining data sent back to Earth by the Messenger probe, the team found that the dark colouration was due to the presence of carbon, with Mercury having high levels than any other planets or their moons.

The discovery of carbon on Mercury was an unexpected one, so much so that none of the instruments on Messenger were designed to detect the element. Instead, Peplowski and his colleagues had to use multiple instruments to identify the carbon.

Need for continued planetary exploration

The discovery gives weight to a theory on how Mercury was formed. The carbon-rich material was detected underneath younger volcanic materials that make up Mercury’s present day surface. This suggests that early Mercury’s original carbon-rich crust may have been formed from graphite that floated to the top of a global magma ocean.

These primordial “floating crusts” provide a rare perspective on early planetary formation.

“This is interesting because the original crusts of the other planets were destroyed long ago by processes like volcanic resurfacing, plate tectonics and erosion,” Peplowski told The Conversation.

“The carbon we see today may be the remains of that ancient, 4.5 billion-year-old crust.”

However, there are still questions as to how the planetary crust was originally formed and why carbon was found around some craters and not others.

“There is a lot of follow-on work to be done,” said Peplowski. “Future missions to Mercury might benefit from instrumentation specifically designed to map carbon in order to follow up on this result.”

The next planetary exploration of Mercury could provide further answers, with the European Space Agency launching the BepiColumbo probe to Mercury next year.

“It has an entirely new suite of instruments that can add to our understanding of carbon on Mercury.”

Planetary puzzles

Dr Helen Maynard-Casely, an Instrument Scientist from the Australian Nuclear Science and Technology Organisation, who was not involved in the study, said the study sheds light on some longstanding mysteries in planetary science.

She added that the theory they study suggests that how Mercury evolved shares many similarities to the early formation of the Moon.

“The early crust of the Moon was made of lighter minerals. It is thought these were stripped off the Earth. In terms of planetary formation, these minerals are like froth on a coffee. Then, as the surface of the Moon has evolved, impacts and lava flows have brought the darker material onto the faces of the Moon,” she said.

“What they’re seeing is that this darker material on Mercury is the remnants of the early frothy material. Graphite is light compared to the other materials on Mercury. They suggest this rose to the top at the very beginning of the planet’s formation creating the first crust of Mercury as it was cooling down.”

But throughout the life of Mercury in the solar system, repeated impacts had churned up the crust, leaving very little of the early surface intact.

Maynard-Casely says that the discovery came as a surprise and may change our view on the how the solar system was formed, and the current model of predicting the presence of carbon, including here on Earth.

“Carbon’s been a very tricky element to pin down, even on Earth, and it is a puzzle to discover what has happened to our carbon. There’s a thought now that a lot of the carbon on Earth is trapped further down within the interior and that we are missing a lot of minerals. There is currently a bit of a worldwide hunt for these,” she said.

“The knowledge of carbon’s significance on Mercury would bring those questions back to the forefront and reinvigorate discussions.”

Ivy Shih, Editor, The Conversation

This article was originally published on The Conversation. (Reblogged by permission). Read the original article.

 

Brian Cox on Apollo 11 moon landing

“I’ve said it before and I’ll say it again – if you don’t think Apollo 11 landed on the Moon you are a colossal nob end and should get a new brain.” – Professor Brian Cox, on the 46th anniversary of the Apollo 11 moon landing.

Beyond Pluto: New Horizons’s mission is not over yet

Jonti Horner, University of Southern Queensland and Jonathan P. Marshall, UNSW Australia

When New Horizons phoned home this morning (Australian time) after its close encounter with Pluto, there was jubilation and excitement.

Now, as Pluto retreats into the distance, the slow trickle of data can begin. Sent to us at a rate of just 1 kilobit a second, it will take months to receive it all, and astronomers around the world are waiting on tenterhooks to get their hands on the data.

Pluto: Once shattered, twice shy

Like our own Earth, Pluto has an oversized satellite, Charon. It was discovered back in 1978 and is more than half the diameter of its parent.

Over the past few years, intense observation of Pluto in preparation for New Horizons’ arrival has revealed four more tiny satellites, Hydra and Nix, and tiny Kerberos and Styx.

Prior to New Horizons, our best view of the Pluto system came from the Hubble Space Telescope. NASA, ESA, and L Frattare (STScI)

But how did this satellite system come to be? And why the striking similarity to our double-planet?

If we look at the great majority of satellites in our solar system we find that they can be split into two groups. First, have those that we think formed around their host planet like miniature planetary systems, mimicking the process of planet formation itself.

These regular satellites most likely accreted from disks of material around the giant planets as those planets gobbled up material from the proto-planetary disk from which they formed. This explains the orbits of those satellites – perfectly aligned with the equator of their hosts and moving on circular orbits.

Then we have the irregular satellites. These are (with a couple of noteworthy exceptions) tiny objects, and move on a wide variety of orbits that are typically great distances from their host planets.

These, too, are easily explained – thought to be captured from the debris moving around the solar system late in its formation, relics of the swarm of minor bodies from which the planets formed.

NASA graphic using New Horizons’ early pictures of Pluto and Charon to compare their sizes to that of the Earth. NASA

By contrast, our moon and Pluto’s Charon are far harder to explain. Their huge size, relative to their host, argues against their forming like the regular satellites. Likewise, their orbits are tilted both to the plane of the equator and to the plane of the host body’s orbit around the sun. It also seems very unlikely they were captured – that just doesn’t fit with our observations.

The answer to this conundrum, in both cases, is violent.

Like our moon, Charon (and by extension Pluto’s other satellites) are thought to have been born in a giant collision, so vast that it tore their host asunder. This model does a remarkable job of explaining the makeup of our own moon, and fits what we know (so far) about Pluto and its satellites.

Pluto and its moons will therefore be the second shattered satellite system we’ve seen up close, and the results from New Horizons will be key to interpreting their formation.

Schematic describing our best theory for the formation of Pluto’s satellite system. Wikimedia/Acom

Studying the similarities and differences between Pluto and Charon will teach us a huge amount about that ancient cataclysmic collision. We already know that Pluto and Charon are different colours, but the differences likely run deeper.

If Pluto was differentiated at the time of impact (in other words, if it had a core, mantle and crust, like the Earth) then Charon should be mostly comprised of material from the crust and mantle (like our moon). So it will be less dense and chemically different to Pluto. The same goes for Pluto’s other moons: Nix, Hydra, Styx and Kerberos.

Pluto, the unknown

The most exciting discoveries from New Horizons will likely be those we can’t predict. Every time we visit somewhere new, the unexpected discoveries are often the most scientifically valuable.

Jupiter and its volcanic moon Io, taken by New Horizons as it tore past the giant planet en-route to Pluto.
NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute/Goddard Space Flight Center

When we first visited Jupiter, 36 years ago, we found that its moon Io was a volcanic hell-scape. We also found that Europa hosts a salty ocean, buried beneath a thick ice cap. Both of these findings were utterly unexpected.

The Death Star terrorised peaceful planets before Voyager sent back images of Mimas. Flickr/Paul T, CC BY

At Saturn, we found the satellite Mimas looked like the Death Star and another, Iapetus, like a two tone cricket ball, complete with a seam. Uranus had a satellite, Miranda, that looked like it had been shattered and reassembled many times over, while Neptune’s moon Triton turned out to be dotted with cryo-volcanoes that spew ice instead of lava.

The story continues for the solar system’s smaller bodies. The asteroid Ida, visited by Galileo on its way to Jupiter, has a tiny moon, Dactyl. Ceres, the dwarf planet in the asteroid belt, has astonishingly reflective bright spots upon its surface.

Pluto, too, will have many surprises in store. There have already been a few, including the heart visible in the latest images (see top) – possibly the most eye catching feature to date. The best is doubtless still to come.

To infinity, and beyond!

Despite the difficulties posed by being more than four and a half billion kilometres from home, New Horizons is certain to revolutionise our understanding of the Pluto system.

The data it obtains will shed new light on the puzzle of our solar system’s formation and evolution, and provide our first detailed images of one of the system’s most enigmatic objects.

But the story doesn’t end there. Once Pluto recedes into the distance, New Horizons will continue to do exciting research. The craft has a limited amount of fuel remaining, nowhere near enough to turn drastically, but enough to nudge it towards another one or two conveniently placed targets.

New Horizons’ will continue its mission after flying past Pluto, studying objects in the Edgeworth-Kuiper belt. NASA

Since the launch of New Horizons, astronomers have been searching for suitable targets for it to visit as it hurtles outward through the Edgeworth-Kuiper belt, en-route to the stars.

In October 2014, as a result of that search, three potential targets were identified. Follow up observations of those objects narrowed the list of possible destinations to two, known as 2014 MU69 (the favoured target) and 2014 PN70.

The final decision on which target to aim for will be taken after New Horizons has left Pluto far behind, but we can expect to keep hearing about the spacecraft for years to come.

Jonti Horner is Vice Chancellor’s Senior Research Fellow at University of Southern Queensland. Jonathan P. Marshall is Vice Chancellor’s Post-doctoral Research Fellow at UNSW Australia.

This article was originally published on The Conversation. (Reblogged by permission). Read the original article.

Live blog: New Horizons flyby of Pluto

Tanya Hill, Museum Victoria

From 9.30pm AEST (12.30pm BST, 1.30pm ASAT, 7.30am EST), I’ll be blogging live as we follow NASA’s coverage of the New Horizons mission. Refresh this page every few minutes for the latest updates.

NASA live stream:

//www.ustream.tv/embed/10414700?v=3&wmode=direct

10:55am, July 15:

New Horizons phones home! Mission control reports that they have locked on to the signal from New Horizons. The team have 15 minutes to check that all systems are healthy. Currently the check-list is running like clockwork, and it is now confirmed that everything is working as it should be. The spacecraft is where it was expected to be – it will have recorded the data they were after. Congratulations NASA.

11:15pm

To finish up for the night – have you checked out Pluto time? I was surprised to find just how bright the daylight is at Pluto. See here to calculate the time at your location that matches the lighting conditions of local noon at Pluto.

The next Pluto time for my location in Melbourne is 7:28am tomorrow, but here’s how it looked a few days ago from the Three Sisters in Katoomba, NSW. The solar system is full of amazing worlds.

10:55pm:

What happens next? The flyby isn’t all that New Horizons is doing. It will now be moving through the shadows of Pluto and Charon. These occultations will allow New Horizons to probe the atmospheres of the two worlds.

When Pluto is between the spacecraft and the sun, measurements will be made at ultraviolet wavelengths to determine what gases are found in Pluto’s atmosphere. Then when Pluto is between the spacecraft and Earth, the aim is for New Horizons to receive a transmission from the NASA’s Deep Space Network on Earth. By detecting how the signal passes through Pluto’s atmosphere it will provide information on the atmospheric pressure and temperature.

 

10:45pm:

Pluto and Charon are a binary world – no other planet and moon combination have such similar masses to each other. Watch this video captured by New Horizons in January and you can see the two objects orbiting around their common centre of mass. Both objects are wobbling back and forth.

Charon and Pluto are also tidally locked – they both keep the same face pointing towards each other. This is because they each take 6.4 Earth days to spin once on their axis AND it takes 6.4 Earth days for Charon to orbit Pluto.

However, they look very different. It appears that Pluto has a younger surface, while Charon is old and battered. As data comes down, scientists will count the number of craters as a function of their size to work out the ages of different parts of their surfaces. Why is Pluto younger? Possibly due to an internal engine or climate effects due to Pluto having an atmosphere, while Charon doesn’t. More will be known with higher resolution data.

10:40pm:

We will get to see the south pole of Pluto, but it’ll be under “Charon-light”. Pluto’s axis is tilted so that the sun set on Pluto’s south pole 20 years ago and it will not rise again for another 80 years. Shortly after New Horizons’ closest approach to Pluto (perhaps happening right now!), the spacecraft will see Pluto’s night-side.

From the surface of Pluto, Charon appears seven times larger than Earth’s full moon, but five times fainter. But that’s enough for Charon to light Pluto so that this southern region will be seen. However, it won’t be as high resolution as the day-time images.

10:30pm:

Here’s the image again:

The north pole is towards the top of the image, while the darker regions towards the bottom are the equator. There is clearly strong variations in brightness across the dwarf planet. The scientists report that they can also see a history of impacts and surface activity, perhaps tectonic activity that occurred in the past or maybe the present.

The atmosphere also plays a role in shaping the planet – it’s known to snow on Pluto and changes have been detected as the planet varies its distance from the sun. But no plumes or other signs of Pluto’s atmosphere have been found, yet.

10:20pm:

Astronaut and astronomer John Grunsfeld (and a hero of mine!) reveals the first of many rewarding views of Pluto. As shown in the sneak peek below, the resolution is 4km per pixels, which is 1,000 times better than can be done from Earth.

But better is to come. Below is a comparison of what Earth would look like if New Horizons was flying over our planet at the same altitude that it has flown by Pluto. In the satellite image looking down on New York city, you can see Manhattan between the Hudson and East rivers, distinguish ponds in Central Park, count the wharves on the Hudson river and see runways from the airport.

Already Pluto is showing features that make it an interesting world to explore.

NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

10:10pm:

Earlier today the New Horizons team provided the best measurement of Pluto’s diameter. At 2,370km, it confirms that Pluto is bigger than the dwarf planet Eris by a mere 34km. When Eris was discovered in 2003, its brightness suggested that it was bigger than Pluto and while the two are now known to be pretty close in size, Eris is certainly more massive by 27%.

Of course the exciting thing about discovering Eris, is that’s opened up a whole new part of the Solar System – a third zone of icy worlds that contain the building blocks of the solar system in deep freeze.

The three zones of the Solar System: the small terrestrial planets, the gas giants and the icy worlds beyond Neptune.
NASA

9:51pm:

New Horizons makes history – somewhere out there, billions of kilometres from Earth a little spacecraft has flown by a distant world. It’s collecting a treasure trove of data that will come flowing back to us over the next year or so. Congratulations to all the scientists, engineeers and those involved that have made it happen.

The team celebrates together.
NASA

9:45pm:

New Horizons is all alone, firing off commands that have been pre-programmed. The last signal from the spacecraft was received at 1:17pm today (AEST). Right now the spacecraft is focused on Pluto – if it spent time talking to Earth that would take time away from observing Pluto. The spacecraft is due to send its ‘I’m fine and healthy’ message back to Earth at 10:53am tomorrow (AEST).

9:40pm:

Here’s a sneak peek of the latest image, taken 6am this morning (AEST) at a distance of 766,000km. Will be discussed on NASA TV in 20 minutes.

9:30pm:

Then and now. Here’s the discovery image of Charon from 1978. See the slight elongation of Pluto in the left image? That gave Charon away, because none of the background stars were found to change in a similar way between the two images.

1978: Pluto and Charon
US Naval Observatory

And this is what New Horizons is giving us now. We see two very different worlds, one large and red, one small and grey.

2015: Pluto and Charon
NASA-JHUAPL-SWRI

9:10pm:

For most of my childhood, Pluto was closer to the sun than Neptune. Pluto takes 248 years to orbit the sun but for 20 years, between January 1979 and February 1999, Pluto sat inside Neptune’s orbit. Even though their orbits cross paths, the two will never collide. They are in a 3:2 resonance, meaning that for every two orbits of Pluto, Neptune has orbited the sun three times, keeping them apart.

8:50pm:

Not asleep now! For about two-thirds of its flight, New Horizons was powered down and in hibernation. Like a real sleepy-head, the spacecraft would briefly wake up two or three times a year, check that all was ok, then return to deep slumber. The spacecraft woke for good on December 6, 2014.

7:30pm:

The road ahead for New Horizons – note the timings are given in Australian Eastern Standard Time (AEST).

 

7:00pm:

“It feels like you’ve been walking on an escalator for almost a decade, and then you step upon a supersonic transport” says Alan Stern, principal investigator for the New Horizons mission to Pluto.

It’s been a long wait for these scientists and engineers, following a spacecraft that was launched nine-and-a-half years ago. It’s no wonder this has been dubbed the mission of patience.

But now, the fun is about to begin. This evening (Australian time), New Horizons will whizz past Pluto – the last unexplored world in our solar system. It’s a new realm of discovery, seeing a part of the solar system that we’ve never seen before. This is a fantastic story of exploration and one we can all be a part of.

Until then, enjoy some of the latest images to be beamed back from the edge of the solar system.

Tanya Hill is Honorary Fellow of the University of Melbourne and Senior Curator (Astronomy) at Museum Victoria.

This article was originally published on The Conversation. (Reblogged by permission). Read the original article.

New Horizons close encounter with Pluto will reveal its icy secrets

Jonti Horner, University of Southern Queensland and Jonathan P. Marshall, UNSW Australia

At around 10 pm AEST on Tuesday July 14, the New Horizons spacecraft will sweep past the dwarf planet Pluto at a distance of less than 12,500 kilometres. In doing so, it will bring one of humankind’s most remarkable achievements to a thrilling climax.

Despite years of preparation, and the nine and a half years the spacecraft has been in flight, this will be the most fleeting of encounters. New Horizons will zip past Pluto faster than a speeding bullet, spending less than 40 hours within a million kilometres of its icy target.

A NASA computer simulation showing New Horizons’ path past Pluto.

Flung towards Pluto by a fortuitous slingshot

New Horizons is a remarkable spacecraft. It is the fastest spacecraft ever launched, and took advantage of a fortunate alignment of the planets to reach its destination in a timely manner.

New Horizons’ trip to the outer solar system began in 2006, and was boosted by a gravitational slingshot by Jupiter, which was ideally placed to give New Horizons a helping hand.

The path followed by New Horizons to reach Pluto.
http://pluto.jhuapl.edu/Mission/Where-is-New-Horizons/index.php

This flyby cut several years from the probe’s trip to the outer reaches of the solar system. Had it been launched just a few days later, the opportunity would have been lost, and New Horizons would have had to take a much slower route to its destination.

As a result of this game of celestial pinball, New Horizons is now placed to tear past Pluto at a relative speed of some 14 kilometres per second. To make the best of this brief encounter with the solar system’s most famous dwarf planet, it carries a veritable Swiss army knife of scientific instruments.

Seven instruments

To get the best possible views of Pluto, and return the most valuable data, New Horizons has been kitted out with seven separate instruments.

The most well known of these is the Long Range Reconnaissance Imager (LORRI), a telescopic camera that has been returning black and white images of ever-increasing detail over the past months. Complementary to LORRI is Ralph, a visible and infrared camera, adding colour to reveal Pluto’s Mars-esque reddish hue.

A colour image of Pluto taken by LORRI and Ralph on July 3rd, eleven days before closest approach. NASA

Map of Pluto, released on July 7, 2015, based on data from LORRI and Ralph.
http://pluto.jhuapl.edu/Multimedia/Science-Photos/image.php?gallery_id=2&image_id=204

Moving from Pluto’s surface to its atmosphere, we come to Alice. This ultraviolet spectrograph will sample the composition of Pluto’s tenuous atmosphere, and also yield details of the surfaces of Pluto and its satellites, working hand-in-hand with Ralph.

While Alice studies the atmosphere at ultraviolet wavelengths, it will be complemented by the Radio Science Experiment (REX), which will carry out a variety of different experiments through the course of the encounter.

Most excitingly, it will use radio signals from Earth to measure both the temperature and composition of Pluto’s atmosphere at radio wavelengths. By using signals from Earth, REX will be able to sample the most tenuous outer layers of the atmosphere, invisible to Alice and Ralph.

The various instruments being carried by New Horizons. NASA

The next pair of complementary instruments carried by New Horizons are Solar Wind At Pluto (SWAP) and Pluto Energetic Particle Spectrometer Science Investigation (PEPSSI). These will work together to capture and study particles bleeding to space from the outer edges of Pluto’s atmosphere.

By sniffing Pluto’s escaping gas, they will determine its composition with exquisite precision. They will also help us to understand how Pluto’s atmosphere interacts with the Solar wind, which is continually streaming outwards from our beloved Sun.

Last, but by no means least, is the Student Dust Counter (SDC). This instrument, wholly designed and run by students, keeps track of interplanetary debris striking New Horizons as it flies ever outward.

The Zodiacal Light – dust in the Solar system – as seen from ESO’s Very Large Telescope, at Paranal Observatory, Chile. Dust suffuses our Solar system,
and the SDC continually measures it throughout  New Horizons’ flight.  ESO/Y. Beletsky

Unlike the other experiments aboard New Horizons, the SDC has remained awake for the entire duration of the mission. In the process, it has continually monitored dust levels during the voyage. This has provided a unique picture of the dust spread throughout the solar system.

A brief encounter, slowly retold

During the flyby, the spacecraft will gather vast amounts of data. This will range from exquisite images to spectra revealing the makeup of Pluto’s atmosphere and surface. But New Horizons is now so distant that we won’t get to see the data in real time.

Data transmitted by New Horizons faces a lengthy journey back home. Travelling at the speed of light, communication takes almost five hours, one way! And it gets worse.

The great distance begets another problem: low bandwidth. Data returned by New Horizons will trickle back at just one kilobit per second. That’s slower than the speed of the internet during the era of the dial-up modem.

As a result, data obtained during closest approach will take around nine months to be wholly transmitted to Earth.

Not all plain sailing

An excellent illustration of the difficulties involved with missions such as this came earlier this week, on July 4. All of a sudden, as though suffering stage fright with the eyes of the world upon it, New Horizons fell asleep.

This was no planned power nap. Communications with ground control ceased unexpectedly, as the spacecraft went into sleep mode, then switched to its backup computer. There was about an hour and 20 minutes of uncertainty and stress before communications were finally restored.

The cause? The central computer overloaded while simultaneously trying to prepare for new observations and to compress data it had already collected for transmission back home.

The main computer responded by entering safe mode, and switching to the backup, just as it was programmed to do. So while the glitch was unexpected, it wasn’t a catastrophe, although doubtless the staff at mission control had an anxious 80 minutes.

Fortunately, everything is now back online and functioning perfectly, and with any luck, there won’t be any more unplanned naps from our plucky little adventurer.

Jonti Horner is Vice Chancellor’s Senior Research Fellow at University of Southern Queensland. Jonathan P. Marshall is Vice Chancellor’s Post-doctoral Research Fellow at UNSW Australia.

This article was originally published on The Conversation. (Reblogged by permission). Read the original article.

NASA mission brings Pluto into sharp focus – but it’s still not a planet

David Rothery, The Open University

The new pictures that NASA’s New Horizons probe has begun to beam back have revealed Pluto and its largest moon, Charon, in ever greater detail from what is the first ever spacecraft fly-by.

Pluto has an atmosphere and five known moons which have been glimpsed by New Horizons as it closes in, and while we can’t predict what we will find, whatever is revealed is sure to lead to renewed cries that Pluto be re-classified as a planet – a status it lost in 2006.

Two sides of Pluto (larger and browner) and Charon (smaller and greyer) seen as New Horizons approaches. NASA/John Hopkins University APL/SWRI

Pluto was embraced as the solar system’s ninth planet upon discovery by Clyde Tombaugh in 1930. He’d been looking for a planet where faulty data suggested a planet-sized body was perturbing the orbit of Neptune. This, he felt, was it – and the world agreed. Pluto’s mass was at first thought to be roughly the same as the Earth’s, but by 1948 estimates had shrunk it to the size of Mars.

When Pluto’s largest moon Charon was discovered in 1978, Charon’s orbit showed that Pluto’s mass is actually about only 0.2% of the Earth’s (one-sixth that of the Moon), and we now know that its diameter is about 2368km, or two-thirds that of the Moon.

Being so insubstantial, then, should Pluto be classed as a planet? There may seem no obvious reason why not. After all, the Earth is only 0.3% the mass of Jupiter. Planets clearly span a wide range of masses. But the main reasons why delegates to the International Astronomical Union (IAU) voted to demote Pluto from planet status are not based primarily on mass or size.

Pluto is one of many

Since the 1990s, many other roughly Pluto-sized bodies have been discovered beyond Neptune, such as Eris, Huamea and Makemake. There are more than a thousand objects now documented in what is called the Kuiper belt, a region beyond Neptune where it seems no large objects were able to form.

If Pluto had been discovered along with the others rather than 60 years earlier, there can be little doubt that no one would have called it a planet in the first place. There is nothing special about Pluto, other than the accident of having been the first to be discovered.

Eight of the so-called trans-Neptunian objects, including Pluto, and their moons. Lexicon

The crucial part of the definition of planet adopted by the IAU in 2006 is that a planet should have “cleared the neighbourhood of its own orbit”. Neptune, 8,600 times more massive than Pluto, has achieved this because neither Pluto nor anything else that crosses Neptune’s orbit comes close to rivalling Neptune’s mass. On the other hand Pluto clearly does not comply to this definition – it has rivals of comparable mass in addition to being overshadowed by the vastly more massive Neptune.

While it may be that this definition is hard to apply in other solar systems, it works for ours and is a far neater approach than including every Kuiper belt object as a planet – thousands of them, which would be ridiculous. The alternative of defining a size or mass minimum at which an object ceases to be a planet would suffer from our variable and imperfect ability to measure their size or mass remotely.

The Kuiper belt is a busy place. NASA/Johns Hopkins University APL/SRI/Alex Parker

A linguistic fudge

Nevertheless, the IAU shied away from completely stripping the Pluto of its appellation of planet by inventing a new term, dwarf planet. This denotes an object orbiting the sun that has not cleared its orbit, but which has sufficient mass for its own gravity to have pulled it into a near-spherical shape (described as hydrostatic equilibrium). This applies to Pluto, Eris and a few other Kuiper belt objects, and also to the largest asteroid, Ceres.

‘Pluto a planet, Jim? You’ve got to be kidding me.’ NBC Television

I think that was an unnecessary concession to the Pluto-is-a-planet lobby, though it proves that the IAU is not controlled by “a clique of Pluto-haters” as one astronomer has claimed. In fact it’s messy for two reasons. First, shapes cannot be precisely determined for objects that have not been visited by a spacecraft; they have to be assumed on the basis of mechanical models that could easily be wrong. Second, whereas the giant planets (Jupiter, Saturn, Uranus and Neptune) are planets, by the IAU’s own definition the dwarf planets are not planets. As Mr Spock might have said, “That’s illogical, Captain.”

Planetary scientists have a duty to describe the nature of the solar system as clearly as possible, and to lead the public to a clearer understanding of nature – irrespective of how its elements are classified. Appealing to sentiment, seeking celebrity endorsement and posting photos of presidential candidates with “Pluto is a planet” T-shirts is not a good way to advance anyone’s understanding. It’s time to let go of the past, and embrace Pluto as a fascinating world and the most interesting member of the Kuiper belt.

David Rothery is Professor of Planetary Geosciences at The Open University.

This article was originally published on The Conversation. (Reblogged by permission). Read the original article.

We Are Dead Stars

Dr. Michelle Thaller (born c. 1970 in Waukesha, Wisconsin) is an American astronomer and research scientist. She is the assistant director for Science Communication at NASA’s Goddard Space Flight Center.

From Mercury to Pluto: the year ahead in planetary exploration

By Donna Burton, University of Southern Queensland

2015 is already shaping up to be a big year in astronomy and planetary exploration, with the best yet to come. Here are some highlights to keep your eye on throughout the year.

Opportunity

January 25 marked 11 years since the Opportunity Rover landed on Mars in 2004 just three weeks after its now inactive twin Spirit. This view is taken from the rim of the Endeavour Crater at a point known as Cape Tribulation.

Opportunity ’s view from Cape Tribulation on the rim of Endeavour Crater, January 22, 2015
NASA/JPL-Caltech/Cornell Univ./Arizona State Univ

This is the highest point that the rover Opportunity has reached since it left the Victoria Crater area back in 2008. It has taken three years for the 180kg solar powered robot to complete the journey down to the Endeavour Crater, which measures 22 kilometres in diameter.

One of its key mission accomplishments has been the characterisation of soft rocks and soil to provide evidence of past water on the Mars. Asteroid 39392 Opportunity was named after this hardworking rover.

Dawn probe

This animation of the dwarf planet Ceres was made by combining images taken by NASA’s Dawn spacecraft on January 25, 2015.
NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Later this year in March, the NASA probe Dawn will arrive at the dwarf planet Ceres. Ceres is one of the largest known bodies in the asteroid belt. It is thought that favourable conditions for life may have once existed there, and the presence of water has recently been announced.

NASA also recently released amazing results from the Dawn mission about the asteroid Vesta. This asteroid was believed to be dry, since it was believed that asteroids are incapable of retaining water.

Yet the recent results provide evidence that Vesta may have had short-lived flows of water-mobilised material on its surface. These results make the asteroid very interesting as these characteristics were thought only to be present on planets. Who knows what interesting discoveries will be made with the upcoming rendezvous with Ceres?

MESSENGER to Mercury

Alver crater graces this image of Mercury’s limb. Secondary crater chains that scour the surface and lead toward the top right of the scene appear to be from the Rembrandt basin to the north.
NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

The MESSENGER ((Mercury Surface, Space Environment, Geochemistry, and Ranging Mission) to Mercury was due to end in March 2015. Launched on August 3, 2004, it entered orbit around Mercury on March 17, 2011, for a one-year discovery mission, and has provided unprecedented views of the innermost planet.

A manoeuvre on January 21 increased the altitude of its orbit, prolonging the mission for possibly another month. Sometime in late April, the probe will descend and crash into the surface of Mercury.

Happy 25th Hubble

The Hubble Space Telescope in a picture snapped by a Servicing Mission 4 crewmember just after the Space Shuttle Atlantis captured Hubble with its robotic arm on May 13, 2009.
NASA

The Hubble Space Telescope turns 25 on April 25, 2015.

Launched into space on the Shuttle Discovery in 1990, and in spite of early problems and repairs over the years, it is still going strong. It is expected to continue through to 2018 when the James Webb Telescope is launched.

New Horizons

Artist’s concept of the New Horizons spacecraft as it approaches Pluto and its three moons in summer 2015.
Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute (JHUAPL/SwRI)

My favourite event will occur on July 14 when NASA’s New Horizons spacecraft flies by Pluto and Charon.

The probe left Earth in 2006, just after Pluto was demoted to being a dwarf planet. It will provide us with the first up close and personal images of this outer solar system object. Initial observations started in January, but the best views will occur as it flies by the dwarf planet on July 14 before heading off to visit other objects far out in the Kuiper Belt.

Rosetta

Mosaic of four images taken by Rosetta’s navigation camera on 22 January 2015 at 28.0 km from the centre of comet 67P/Churyumov-Gerasimenko.
ESA/Rosetta/NAVCAM, CC BY-SA

Rosetta successfully launched the Philae lander onto the surface of Comet 67P/Churyumov-Gerasimenko on November 2014 and continues to orbit the comet as it makes closest approach to the sun on 13 August 2015.

Rosetta’s mission is to monitor how the comet changes as it approaches the sun. It is hoped that the Philae lander, currently in hibernation, will wake up in the early months of the year as it gets more sunlight on its solar panels and again gather data.

Cassini meets Enceladus

This view looks across the region of Enceladus’ geyser basin and down on the ends of the Baghdad and Damascus fractures that face Saturn.
NASA/JPL-Caltech/Space Science Institute

In October NASA’s Cassini mission is scheduled to undertake a close flyby of Saturn’s moon Enceladus.

The flyby will allow the spacecraft to get close enough to fly through the geysers of water that have been discovered emanating from this very interesting icy moon and hopefully reveal secrets of a possible subsurface ocean.

Goodbye Voyager 2

Artist’s impression of Voyager departing our solar system and entering deep space.
NASA/JPL

2015 will also see Voyager 2 follow its younger sibling out past the edge of our solar system sometime during this year.

Both Voyager spacecraft were launched in 1977 and, with Pioneer 10, are now the most distant man-made objects in the solar system. While Pioneer 10, launched in 1972, has not been contactable since 2003, both Voyager probes continue to send information.

This is just a snapshot of some of the highlights of 2015, which is sure to be a momentous year in space exploration.

This article was originally published on The Conversation. (Reblogged by permission). Read the original article.