ESA Rosetta: Earth's Water Came from Asteroids, Not Comets

ESA Rosetta’s navigation camera obtained the four images in this mosaic on Dec. 7, 2014, from a distance of 12.2 miles (19.7 km) from the center of Comet 67P/Churyumov-Gerasimenko.

Credit: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0

Asteroids, not comets, may have delivered most of Earth's water to the planet when the solar system was young, new data from the ESA Rosetta probe orbiting comet 67/P suggests.

Comets are some of the solar system's most primitive building blocks, with many dating to soon after its formation.

Scientists think that these dirty snowballs probably helped seed Earth with key ingredients for life, such as organic compounds.

The European Space Agency's (ESA) Rosetta spacecraft is helping scientists learn more about the role these icy nomads have played in the evolution of the solar system and life on Earth by analyzing the composition of Comet 67P/Churyumov–Gerasimenko.

In August, Rosetta became the first spacecraft to orbit a comet, and in November, its Philae lander became the first probe to make a soft touchdown on a comet's surface.

Rosetta is also the first mission to escort a comet as it travels around the sun.

Now, Rosetta has helped solve a mystery about how Earth became the watery world it is today.

Before Rosetta began orbiting Comet 67P/C-G in August, it was using an instrument known as ROSINA (short for Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) to analyze the chemical fingerprint of gases in the comet's fuzzy envelope.

Scientists focused on data from the instrument regarding water to help uncover whether asteroids or comets delivered the water in Earth's oceans.

Rosetta has provided data from Comet 67P/C-G, another Kuiper Belt comet.

However, Rosetta has discovered that this comet possesses an even higher deuterium-to-hydrogen ratio than seen in Oort Cloud comets, three times the amount of heavy water compared to normal water as Earth has.

If Earth's water had come from Kuiper Belt objects, even if most of them were like comet 103P/Hartley 2, and if only a small fraction were like Comet 67P/C-G, Earth's deuterium-to-hydrogen ratio would be significantly higher than it is today.

"This probably rules out Kuiper Belt comets from bringing water to Earth," Altwegg said. Instead, most of Earth's water was probably delivered by asteroids, Altwegg said.

"Today's asteroids have very little water, that's clear," Altwegg added. "But that was probably not always the case. During the Late Heavy Bombardment 3.8 billion years ago, at that time, asteroids could have had much more water than they could now."

The asteroids seen now "have stayed in the vicinity of the sun for 4.6 billion years," Altwegg said.

"They've lost water due to the sun, due to heat. But to start with, they might have had much more water than they have now."

Future analysis of ice-rich bodies in the asteroid belt could shed light on whether Earth's water really did come from there, Altwegg said.

NASA Science Fleet: Comet Siding Spring C/2013 A1

Credit: NASA

NASA's extensive fleet of science assets, particularly those orbiting and roving Mars, have front row seats to image and study a once-in-a-lifetime comet flyby on Sunday, Oct. 19.

Comet C/2013 A1, also known as comet Siding Spring, will pass within about 87,000 miles (139,500 kilometers) of the Red Planet, less than half the distance between Earth and our moon and less than one-tenth the distance of any known comet flyby of Earth.

Siding Spring's nucleus will come closest to Mars around 2:27 p.m. EDT, hurtling at about 126,000 mph (56 kilometers per second).

This proximity will provide an unprecedented opportunity for researchers to gather data on both the comet and its effect on the Martian atmosphere.

"This is a cosmic science gift that could potentially keep on giving, and the agency's diverse science missions will be in full receive mode," said John Grunsfeld, astronaut and associate administrator for NASA's Science Mission Directorate in Washington.

"This particular comet has never before entered the inner solar system, so it will provide a fresh source of clues to our solar system's earliest days."

Siding Spring came from the Oort Cloud, a spherical region of space surrounding our sun and occupying space at a distance between 5,000 and 100,000 astronomical units.

It is a giant swarm of icy objects believed to be material left over from the formation of the solar system.

Siding Spring will be the first comet from the Oort Cloud to be studied up close by spacecraft, giving scientists an invaluable opportunity to learn more about the materials, including water and carbon compounds, that existed during the formation of the solar system 4.6 billion years ago.

Some of the best and most revealing images and science data will come from assets orbiting and roving the surface of Mars.

Mars Atmosphere and Volatile EvolutioN (MAVEN)

In preparation for the comet flyby, NASA maneuvered its Mars Odyssey orbiter, Mars Reconnaissance Orbiter (MRO), and the newest member of the Mars fleet, Mars Atmosphere and Volatile EvolutioN (MAVEN), to reduce the risk of impact with high-velocity dust particles coming off the comet.

The period of greatest risk to orbiting spacecraft will start about 90 minutes after the closest approach of the comet's nucleus and will last about 20 minutes, when Mars will come closest to the center of the widening trail of dust flying from the comet's nucleus.

"The hazard is not an impact of the comet nucleus itself, but the trail of debris coming from it. Using constraints provided by Earth-based observations, the modeling results indicate that the hazard is not as great as first anticipated."

"Mars will be right at the edge of the debris cloud, so it might encounter some of the particles, or it might not," said Rich Zurek, chief scientist for the Mars Exploration Program at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California.

The atmosphere of Mars, though much thinner that Earth's, will shield NASA Mars rovers Opportunity and Curiosity from comet dust, if any reaches the planet. Both rovers are scheduled to make observations of the comet.

NASA's Mars orbiters will gather information before, during and after the flyby about the size, rotation and activity of the comet's nucleus, the variability and gas composition of the coma around the nucleus, and the size and distribution of dust particles in the comet's tail.

Observations of the Martian atmosphere are designed to check for possible meteor trails, changes in distribution of neutral and charged particles, and effects of the comet on air temperature and clouds.

MAVEN will have a particularly good opportunity to study the comet, and how its tenuous atmosphere, or coma, interacts with Mars' upper atmosphere.

Earth-based and space telescopes, including NASA and ESA's iconic Hubble Space Telescope, also will be in position to observe the unique celestial object.

The agency's astrophysics space observatories, Kepler, Swift, Spitzer, Chandra, and the ground-based Infrared Telescope Facility on Mauna Kea, Hawaii, also will be tracking the event.

NASA's asteroid hunter, the Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE), has been imaging, and will continue to image, the comet as part of its operations, and the agency's two Heliophysics spacecraft, Solar TErrestrial RElations Observatory (STEREO) and Solar and Heliophysics Observatory (SOHO), also will image the comet.

The agency's Balloon Observation Platform for Planetary Science (BOPPS), a sub-orbital balloon-carried telescope, already has provided observations of the comet in the lead-up to the close encounter with Mars.

Images and updates will be posted online before and after the comet flyby. Several pre-flyby images of Siding Spring, as well as information about the comet and NASA's planned observations of the event, are available online.

Comet C/2012 K1 PanSTARRS: Two Tails and still going

Comet C/2012 K1 PanSTARRS photographed on September 26, 2014. 

Two tails are seen, a dust tail points off to the left and the gas or ion tail to the right. 

Credit: Rolando Ligustri

Thank you K1 PanSTARRS for hanging in there! Some comets crumble and fade away.

Others linger a few months and move on, but after looping across the night sky for more than a year, this one is nowhere near quitting. Matter of fact, the best is yet to come.

This new visitor from the Oort Cloud making its first passage through the inner solar system, C/2012 K1 was discovered in May 2012 by the Pan-STARRS 1 survey telescope atop Mt. Haleakala in Hawaii.

The orbit of comet K1 PanSTARRS through the inner solar system. 

The yellow arrows denote the motion of the planets and the comet as seen from north of the ecliptic plane. 

Credit-NASA/JPL Horizons Solar System Dynamics generator.

On its the inbound journey from the Oort Cloud, C/2012 K1 approached with an orbit estimated in the millions of years. Perturbed by its interactions with the planets, its new orbit has been reduced to a mere ~400,000 years.

That makes the many observing opportunities K1 PanSTARRS has provided that much more appreciated. No one alive now will ever see the comet again once this performance is over.

Many amateur astronomers first picked up the comet's trail in the spring of 2013 when it had brightened to around magnitude 13.5.

K1 PanSTARRS slowly brightened in Serpens last fall until it was lost in evening twilight. Come January this year it returned to the morning sky a little closer to Earth and Sun and a magnitude brighter.

As winter snow gave way to frogs and flowers, the comet rocketed across Corona Borealis, Bootes and Ursa Major.

Its fat, well-condensed coma towed a pair of tails and grew bright enough to spot in binoculars at magnitude 8.5 in late May.

Comet C/2012 K1 PanSTARRS’ changing appearance over the past year. 

Credit: upper left clockwise: Carl Hergenrother, Damian Peach, Chris Schur and Rolando Ligustri

By July, it hid away in the solar glare a second time only to come back swinging in September's pre-dawn sky.

Now in the constellation Hydra and even closer to Earth, C/2012 K1 has further brightened to magnitude 7.5.

Though low in the southeast at dawn, astronomers were pleasantly surprised to see it several mornings ago.

Mid-northern observers can watch the comet's antics through mid-October. From then on, K1 will only be accessible from the far southern U.S. and points south as it makes the rounds of Pictor, Dorado and Horologium.

After all this time you might think the comet is ready to depart Earth's vicinity but it is not.

C/2012 K1 will finally make its closest approach to our planet on Halloween (88.6 million miles, 143 million km) when it could easily shine at magnitude 6.5, making it very nearly a naked-eye comet.

K1 PanSTARRS's not giving up anytime soon. Southern skywatchers will keep it in view through the spring of 2015 before it returns to the deep chill from whence it came.

After delighting skywatchers for nearly two years, it'll be hard to let this one go.

Skywatchers can find C/2012 K1 PanSTARRS in the morning sky in the Hydra and Puppis just before dawn when it’s highest in the southeastern sky. 

The map shows its location daily with stars to magnitude 8.5. 

The numbers next to some stars are standard Flamsteed atlas catalogue numbers. 

Credit: Chris Marriott’s SkyMap

Dark Matter Disk in Milky Way plane - signaling a rash of comet strikes on Earth

Our Solar System orbits around the Milky Way’s center, completing a revolution every 250 million years or so. 

Along this path, it oscillates up and down, crossing the galactic plane about every 32 million years.

If a dark matter disk were concentrated along the galactic plane, as shown here, it might tidally disrupt the motion of comets in the Oort cloud at the outer edge of our Solar System. 

This could explain possible periodic fluctuations in the rate of impacts on Earth. 

Credit: Physics 7, 41 (2014) | DOI: 10.1103/Physics.7.41

A pair of researchers at Harvard University has published a paper in the journal Physical Review Letters, in which they suggest that a dark matter disk hiding in the Milky Way plane might be responsible for causing asteroids or comets to head our way.

Lisa Randall

In their paper, Lisa Randall and Matthew Reece suggest that such a dark matter disk could pull other bodies from the Oort cloud, some of which could wind up heading toward Earth.

It has been noted by scientists that asteroids and comets tend to strike the Earth in a cyclic pattern that occurs approximately every 35 million, as evidenced by telltale craters but why such a cycle might occur is still up to conjecture.

Some have suggested it's due to a mysterious planet hidden from our view, or perhaps the presence of an as yet undiscovered companion star.

Matthew Reece

In this new effort, the research duo suggests it might be due to the gravitational pull of a dark matter disk residing in the Milky Way Galaxy plane.

This is not the first time that scientists have suggested such a disk might exist, it's been suggested that a dark matter a disk would explain why our galaxy doesn't spin apart.

It is the first time, however, that such a disk has been proposed as an answer to why our planet gets bombarded periodically with asteroids or comets.

In their paper, Randall and Reece note that the conventional view of the material that makes up dark matter, wouldn't work as a means of pulling other bodes from where they currently reside, it's evident in their name, weakly interacting massive particles.

They suggest that some dark matter could be made instead of what they describe as "strong electromagnetic-like interactions among dark matter particles" which by their nature would exert a greater gravitational pull.

And if that were the case, then it would seem plausible that as our solar system circles around the center of our galaxy, most particularly as we move closer to the Oort cloud, some of those bodies that exist there, could be jostled, which in turn could cause some of them to wind up on a collision course with our planet.

This new theory by the research pair has some problems, it assumes the periodicity (?) of crater creation has been firmly established, which it hasn't, and, scientists aren't even sure which craters on the Earth's surface were cause by what sort of object.

In any event, the theory is expected to gain or lose credence as the European Space Agency's Gaia mission gets underway, it's supposed to give us a better view of the Milky Way Galaxy than ever before.

More information: Dark Matter as a Trigger for Periodic Comet Impacts, Phys. Rev. Lett. 112, 161301 – Published 21 April 2014. journals.aps.org/prl/abstract/10.1103/PhysRevLett.112.161301

SEDNA: Dwarf Planet on the outer regions of Solar System

Sedna is a dwarf planet on the far outer reaches of the solar system.

Credit: NASA

Sedna is a dwarf planet that is one of the most distant bodies found in our solar system.

The object's closest approach to the sun is far greater than Pluto's distance away from Earth, at a spot where the sun is so tiny, according to NASA, that you could blot it out with a pin.

At 8 billion miles (12.8 billion kilometers) away, it's hard to figure out things such as surface features, but one thing astronomers have been able to identify is Sedna's distinct reddish colour.

Mike Brown

In 2004, it was described as the second-reddest object in our solar system, after Mars.

Sedna was discovered by a team led by Mike Brown, an astronomer at the California Institute of Technology.

The discovery of Sedna and other objects similar to it was a large impetus behind demoting Pluto from planetary status in 2006.

Image of Sedna, taken by Hubble Space Telescope

Discovery and basic statistics
Brown's team found Sedna in 2003 as part of a larger survey of the solar system that began in 2001.

Using the Samuel Oschin Telescope at the Palomar Observatory (east of San Diego) as well as Palomar's Quasar Equatorial Survey Team (QUEST) camera, the astronomers would take pictures of a tiny spot in the sky, one per hour for three hours, and see if they could find something that moved, Brown said in an explanation page about the discovery.

"The many billions of stars and galaxies visible in the sky appear stationary, while satellites, planets, asteroids, and comets appear to move. Objects in the inner Oort Cloud are extremely distant and so move extremely slowly," he said.

The Oort Cloud expands from a narrow belt on its inner edge
 into a large sphere farther from the Sun.

The Oort Cloud is a theorized area far in the solar system that is supposed to contain billions of icy objects that, if they receive a gravitational push toward the sun and warm up, turn into comets as the sun's energy melts the ice.

Sedna, however, was much bigger than a comet. Estimates for Sedna's size vary, but it is believed to be slightly smaller than the size of Pluto (1,400 miles or 2,250 kilometers in diameter).

Sedna takes some time to orbit the sun, not only because of its vast distance but also because its orbit is so elliptical or oval-shaped.

The dwarf planet takes roughly 10,000 years to complete one circuit around the sun. At the time of its discovery, it was at one of the closest points of its orbit to the sun, making it easier to spot.

Credit: Nasa

More Information: An explanation page about the SEDNA discovery

Gemini Observatory: A new object at the edge of our Solar System

These are the discovery images of 2012 VP113, affectionately called 'Biden' because of the VP in the provisional name. 

It has the most distant orbit known in our Solar System. 

Three images of the night sky, each taken about two hours apart, were combined into one.

The first image was artificially colored red, second green and third blue. 

2012 VP113 moved between each image as seen by the red, green and blue dots. 

The background stars and galaxies did not move and thus their red, green and blue images combine to showup as white sources. 

Credit: Scott Sheppard and Chad Trujillo

The Solar System has a new most-distant member, bringing its outer frontier into focus.

New work from Scott Sheppard of Carnegie and Chadwick Trujillo of the Gemini Observatory reports the discovery of a distant dwarf planet, called 2012 VP113, which was found beyond the known edge of the Solar System.

This is likely one of thousands of distant objects that are thought to form the so-called inner Oort cloud.

What's more, their work indicates the potential presence of an enormous planet, perhaps up to 10 times the size of Earth, not yet seen, but possibly influencing the orbit of 2012 VP113, as well as other inner Oort cloud objects.

Their findings are published March 27 in Nature.

The paper is Sheppard and Trujillo, “A Sedna-like body with a perihelion of 80 astronomical units,” Nature 507 (27 March, 2014), 471-474.

The known Solar System can be divided into three parts: the rocky planets like Earth, which are close to the Sun; the gas giant planets, which are further out; and the frozen objects of the Kuiper belt, which lie just beyond Neptune's orbit.

Beyond this, there appears to be an edge to the Solar System where only one object, Sedna, was previously known to exist for its entire orbit.

But the newly found 2012 VP113 has an orbit that stays even beyond Sedna, making it the furthest known in the Solar System.

"This is an extraordinary result that redefines our understanding of our Solar System," says Linda Elkins-Tanton, director of Carnegie's Department of Terrestrial Magnetism.

These images show the discovery of the new inner Oort cloud object 2012 VP113 taken about 2 hours apart on UT November 5, 2012. 

The motion of 2012 VP113 clearly stands out compared to the steady state background stars and galaxies. 

Credit: Scott S. Sheppard: Carnegie Institution for Science

Sedna was discovered beyond the Kuiper Belt edge in 2003, and it was not known if Sedna was unique, as Pluto once was thought to be before the Kuiper Belt was discovered.

With the discovery of 2012 VP113 it is now clear Sedna is not unique and is likely the second known member of the hypothesized inner Oort cloud, the likely origin of some comets.

2012 VP113's closest orbit point to the Sun brings it to about 80 times the distance of the Earth from the Sun, a measurement referred to as an astronomical unit or AU.

For context, the rocky planets and asteroids exist at distances ranging between .39 and 4.2 AU.

Gas giants are found between 5 and 30 AU, and the Kuiper belt (composed of thousands of icy objects, including Pluto) ranges from 30 to 50 AU.

In our solar system there is a distinct edge at 50 AU. Only Sedna was known to stay significantly beyond this outer boundary at 76 AU for its entire orbit.

More information: Paper: dx.doi.org/10.1038/nature13156

The Solar System: The Kuiper Belt and Oort Cloud

Our solar system is a vast place, with lots of mostly empty space between planets but out there are comets, asteroids and more rocky, frozen objects (including dwarf planets) yet to be discovered in the Kuiper Belt and Oort Cloud.

CREDIT: NASA

NASA's Spirit Rover landed on Mars nine years ago today (Jan. 3), kicking off a surface mission that's still operational thanks to the amazing endurance of Spirit's twin Opportunity.

Mars is currently host to five active space missions, commanding more attention than any planet apart from Earth. But unmanned probes are also exploring many other solar system bodies, from the sun out to Pluto and beyond.



Solar Terrestrial Relations Observatory: NASA's $550 million sun-studying STEREO mission, which blasted off in October 2006, consists of two spacecraft, known as A and B. Both probes are in a heliocentric orbit, with A zipping around the sun faster than Earth and B lagging somewhat behind.