Science Current Events | Science News |

NASA Developing Comet Harpoon for Sample Return

December 14, 2011
The best way to grab a sample of a rotating comet that is racing through the inner solar system at up to 150,000 miles per hour while spewing chunks of ice, rock and dust may be to avoid the risky business of landing on it. Instead, researchers want to send a spacecraft to rendezvous with a comet, then fire a harpoon to rapidly acquire samples from specific locations with surgical precision while hovering above the target. Using this "standoff" technique would allow samples to be collected even from areas that are much too rugged or dangerous to permit the landing and safe operation of a spacecraft.

Scientists at NASA's Goddard Space Flight Center in Greenbelt, Md. are in the early stages of working out the best design for a sample-collecting comet harpoon. In a lab the size of a large closet stands a metal ballista (large crossbow) nearly six feet tall, with a bow made from a pair of truck leaf springs and a bow string made of steel cable 1/2 inch thick. The ballista is positioned to fire vertically downward into a bucket of target material. For safety, it's pointed at the floor, because it could potentially launch test harpoon tips about a mile if it was angled upwards. An electric winch mechanically pulls the bow string back to generate a precise level of force, up to 1,000 pounds, firing projectiles to velocities upwards of 100 feet per second.

Donald Wegel of NASA Goddard, lead engineer on the project, places a test harpoon in the bolt carrier assembly, steps outside the lab and moves a heavy wooden safety door with a thick plexiglass window over the entrance. After dialing in the desired level of force, he flips a switch and, after a few-second delay, the crossbow fires, launching the projectile into a 55-gallon drum full of cometary simulant -- sand, salt, pebbles or a mixture of each. The ballista produces a uniquely impressive thud upon firing, somewhere between a rifle and a cannon blast.

"We had to bolt it to the floor, because the recoil made the whole testbed jump after every shot," said Wegel. "We're not sure what we'll encounter on the comet - the surface could be soft and fluffy, mostly made up of dust, or it could be ice mixed with pebbles, or even solid rock. Most likely, there will be areas with different compositions, so we need to design a harpoon that's capable of penetrating a reasonable range of materials. The immediate goal though, is to correlate how much energy is required to penetrate different depths in different materials. What harpoon tip geometries penetrate specific materials best? How does the harpoon mass and cross section affect penetration? The ballista allows us to safely collect this data and use it to size the cannon that will be used on the actual mission."

Comets are frozen chunks of ice and dust left over from our solar system's formation. As such, scientists want a closer look at them for clues to the origin of planets and ultimately, ourselves. "One of the most inspiring reasons to go through the trouble and expense of collecting a comet sample is to get a look at the 'primordial ooze' - biomolecules in comets that may have assisted the origin of life," says Wegel.

Scientists at the Goddard Astrobiology Analytical Laboratory have found amino acids in samples of comet Wild 2 from NASA's Stardust mission, and in various carbon-rich meteorites. Amino acids are the building blocks of proteins, the workhorse molecules of life, used in everything from structures like hair to enzymes, the catalysts that speed up or regulate chemical reactions. The research gives support to the theory that a "kit" of ready-made parts created in space and delivered to Earth by meteorite and comet impacts gave a boost to the origin of life.

Although ancient comet impacts could have helped create life, a present-day hit near a populated region would be highly destructive, as a comet's large mass and high velocity would make it explode with many times the force of a typical nuclear bomb. One plan to deal with a comet headed towards Earth is to deflect it with a large - probably nuclear - explosion. However, that might turn out to be a really bad idea. Depending on the comet's composition, such an explosion might just fragment it into many smaller pieces, with most still headed our way. It would be like getting hit with a shotgun blast instead of a rifle bullet. So the second major reason to sample comets is to characterize the impact threat, according to Wegel. We need to understand how they're made so we can come up with the best way to deflect them should any have their sights on us.

"Bringing back a comet sample will also let us analyze it with advanced instruments that won't fit on a spacecraft or haven't been invented yet," adds Dr. Joseph Nuth, a comet expert at NASA Goddard and lead scientist on the project.

Of course, there are other ways to gather a sample, like using a drill. However, any mission to a comet has to overcome the challenge of operating in very low gravity. Comets are small compared to planets, typically just a few miles across, so their gravity is correspondingly weak, maybe a millionth that of Earth, according to Nuth. "A spacecraft wouldn't actually land on a comet; it would have to attach itself somehow, probably with some kind of harpoon. So we figured if you have to use a harpoon anyway, you might as well get it to collect your sample," says Nuth.

Right now, the team is working out the best tip design, cross-section, and explosive powder charge for the harpoon, using the crossbow to fire tips at various speeds into different materials like sand, ice, and rock salt. They are also developing a sample collection chamber to fit inside the hollow tip. "It has to remain reliably open as the tip penetrates the comet's surface, but then it has to close tightly and detach from the tip so the sample can be pulled back into the spacecraft," says Wegel. "Finding the best design that will package into a very small cross section and successfully collect a sample from the range of possible materials we may encounter is an enormous challenge."

"You can't do this by crunching numbers in a computer, because nobody has done it before -- the data doesn't exist yet," says Nuth. "We need to get data from experiments like this before we can build a computer model. We're working on answers to the most basic questions, like how much powder charge do you need so your harpoon doesn't bounce off or go all the way through the comet. We want to prove the harpoon can penetrate deep enough, collect a sample, decouple from the tip, and retract the sample collection device."

The spacecraft will probably have multiple sample collection harpoons with a variety of powder charges to handle areas on a comet with different compositions, according to the team. After they have finished their proof-of-concept work, they plan to apply for funding to develop an actual instrument. "Since instrument development is more expensive, we need to show it works first," says Nuth.

Currently, the European Space Agency is sending a mission called Rosetta that will use a harpoon to grapple a probe named Philae to the surface of comet "67P/Churyumov-Gerasimenko" in 2014 so that a suite of instruments can analyze the regolith. "The Rosetta harpoon is an ingenious design, but it does not collect a sample," says Wegel. "We will piggyback on their work and take it a step further to include a sample-collecting cartridge. It's important to understand the complex internal friction encountered by a hollow, core-sampling harpoon."

NASA's recently-funded mission to return a sample from an asteroid, called OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, Security -- Regolith Explorer), will gather surface material using a specialized collector. However, the surface can be altered by the harsh environment of space. "The next step is to return a sample from the subsurface because it contains the most primitive and pristine material," said Wegel.

Both Rosetta and OSIRIS-REx will significantly increase our ability to navigate to, rendezvous with, and locate specific interesting regions on these foreign bodies. The fundamental research on harpoon-based sample retrieval by Wegel and his team is necessary so the technology is available in time for a subsurface sample return mission.

The team includes Wegel and Nuth of NASA Goddard as well as Javier Bernal, a student intern from the University of Puerto Rico at Mayaguez. The work was initially funded by Goddard's Internal Research and Development program, and sustained by NASA's Science and Engineering Collaboration, the Undergraduate Student Researcher Program, and Universities Space Research Programs.

NASA's Goddard Space Flight Center

Related Comet Current Events and Comet News Articles

Fresh theories about dark matter
Tom Broadhurst, the Ikerbasque researcher in the Department of Theoretical Physics of the UPV/EHU, together with Sandor Molnar of the National Taiwan University and visiting Ikerbasque researcher at the UPV/EHU in 2013, have conducted a simulation that explains the collision between two clusters of galaxies.

Comet Wild 2: A window into the birth of the solar system?
Our solar system, and other planetary systems, started as a disk of microscopic dust, gas, and ice around the young Sun. The amazing diversity of objects in the solar system today - the planets, moons, asteroids, and comets - was made from this primitive dust.

Geothermal energy, aluto volcano, and Ethiopia's rift valley
In their open access paper published in Geosphere this month, William Hutchison and colleagues present new data from Ethiopia's Rift Valley and Aluto volcano, a major volcano in the region.

Millions of liters of juice from 1 grapefruit
The Austrian Centre of Industrial Biotechnology (acib) uses the positive aspects of synthetic biology for the ecofriendly production of a natural compound.

Complex organic molecules discovered in infant star system
The new ALMA observations reveal that the protoplanetary disc surrounding the young star MWC 480 [1] contains large amounts of methyl cyanide (CH3CN), a complex carbon-based molecule. There is enough methyl cyanide around MWC 480 to fill all of Earth's oceans.

Comet dust: Planet Mercury's 'invisible paint'
A team of scientists has a new explanation for the planet Mercury's dark, barely reflective surface.

World's first method for continuous purification of valuable antibodies
Imagine a loved relative suffering from cancer - and you could not afford a treatment because the drugs are too expensive.

A second minor planet may possess Saturn-like rings
There are only five bodies in our solar system that are known to bear rings. The most obvious is the planet Saturn; to a lesser extent, rings of gas and dust also encircle Jupiter, Uranus, and Neptune.

SOHO sees something new near the sun
An unusual comet skimmed past the sun on Feb 18-21, 2015, as captured by the European Space Agency (ESA) and NASA's Solar and Heliospheric Observatory, or SOHO.

Rosetta mission named Physics World 2014 Breakthrough of the Year
The journal Physics World has named the first landing of a research probe on a comet as its 2014 Breakthrough of the Year.
More Comet Current Events and Comet News Articles


by Carl Sagan (Author)

This book is an exploration of these strange visitors to our skies.

Comet's Tale: How the Dog I Rescued Saved My Life

Comet's Tale: How the Dog I Rescued Saved My Life
by Steven Wolf (Author), Lynette Padwa (Author)

Comet’s Tale is a story about a friendship between two former winners, both a little down on their luck, who together stage a remarkable comeback. A former hard-driving attorney, Steven Wolf has reluctantly left his job and family and moved to Arizona for its warm winter climate. There he is drawn to a local group that rescues abused racing greyhounds. Although he can barely take care of himself because of a spinal condition, Wolf adopts Comet, an elegant cinnamon-striped racer. Or does Comet adopt Wolf?  In Comet’s Tale we follow their funny and moving journey as Wolf teaches Comet to be a service dog. With her boundless enthusiasm and regal manners, Comet attracts new friends to Wolf’s isolated world. And finally, she plays a crucial role in restoring his health, saving his...

Comets, Stars, the Moon, and Mars: Space Poems and Paintings

Comets, Stars, the Moon, and Mars: Space Poems and Paintings
by Douglas Florian (Author)

Blast off with Douglas Florian's new high-flying compendium, which features twenty whimsical poems about space.      From the moon to the stars, from the Earth to Mars, here is an exuberant celebration of our celestial surroundings that's certain to become a universal favorite among aspiring astronomers everywhere.      Includes die-cut pages and a glossary of space terms.

Atlas of Great Comets

Atlas of Great Comets
by Ronald Stoyan (Author), Storm Dunlop (Translator)

Throughout the ages, comets, enigmatic and beautiful wandering objects that appear for weeks or months, have alternately fascinated and terrified humankind. The result of five years of careful research, Atlas of Great Comets is a generously illustrated reference on thirty of the greatest comets that have been witnessed and documented since the Middle Ages. Special attention is given to the cultural and scientific impact of each appearance, supported by a wealth of images, from woodcuts, engravings, historical paintings and artifacts, to a showcase of the best astronomical photos and images. Following the introduction, giving the broad historical context and a modern scientific interpretation, the Great Comets feature in chronological order. For each, there is a contemporary description of...

The Comets Of God-New Scientific Evidence for God: Recent archeological, geological and astronomical discoveries that shine new light on the Bible and its prophecies

The Comets Of God-New Scientific Evidence for God: Recent archeological, geological and astronomical discoveries that shine new light on the Bible and its prophecies
by Jeffrey Goodman (Author)

THE COMETS OF GOD shows that almost all of the large-scale catastrophes described or prophesied in the Bible can be explained as a consequence of cometary phenomena.
Dr. Goodman, an archeologist and geologist, has spent 20 years studying the Bible’s stories and prophecies of catastrophe. His research reveals important scientific information hidden in the Bible. In a process that can be called “Biblical CSI,” Goodman translated the original Hebrew words of the Bible according to their ancient usage, and then related them to recent archeological, geological, and astronomical discoveries. What Goodman discovered were dramatically different explanations for these events than the traditional translations have told. THE COMETS OF GOD documents significant scientific...

Comet!   (an Ell Donsaii story #5 )

Comet! (an Ell Donsaii story #5 )

"Comet!" is the fifth in a series of near future SciFi/Thrillers whose young heroine Ell Donsaii has a nerve mutation which has rendered her a genius and an athletic phenomenon. In “Comet!” she and her team begin exploring outer space using the wormholes she produced in "Rocket." Unfortunately Comet Hearth-Daster is on a trajectory to strike the Earth. Though it is smaller than the object that wiped out the dinosaurs, it still weighs 300 million metric tons and if it hits it will wipe out civilization and may render the human race extinct.


Walking to the machine shop to talk to Manuel, Ell passed behind Brian and Fred walking across the room. A shock went through her. Brian had a pistol in his hand! Horrifying images of a disgruntled employee gone...

Comets: Creators and Destroyers

Comets: Creators and Destroyers
by David H. Levy (Author)

David Levy brings these "ghostly apparitions" to life. With fascinating scenarios both real and imagined, he shows how comets have wreaked their special havoc on Earth and other planets. Beginning with ground zero as comets take form, we track the paths their icy, rocky masses take around our universe and investigate the enormous potential that future comets have to directly affect the way we live on this planet and what we might find as we travel to other planets.
In this extraordinary volume, David Levy shines his expert light on a subject that has long captivated our imaginations and fears, and demonstrates the need for our continued and rapt attention.

The Origin of Comets

The Origin of Comets
by M. E. Bailey (Author), S. V. M. Clube (Author), W. M. Napier (Author)

The Origin of Comets describes the development of nan's concerns about comets in terms of a changing cometary environment from the very earliest times, when astronomical records were first preserved on cuneiform tablets, to the present day. The importance of ideas about comets to other branches of knowledge is emphasized, especially in relation to galactic and terrestrial evolution. This authoritative book, containing more than 1200 literature references, is the first to deal comprehensively with the origin of comets. It has been written with both general readers and committed scientists in mind, and will appeal to amateur and professional astronomers alike. It will be an invaluable source-book for students with historical and environmental interests, particularly in the fields of earth...

In the Days of the Comet

In the Days of the Comet

This book was converted from its physical edition to the digital format by a community of volunteers. You may find it for free on the web. Purchase of the Kindle edition includes wireless delivery.

Final Days (Comet Clement series, #6)

Final Days (Comet Clement series, #6)

With only days remaining until Comet Clement reaches Earth, final preparations are made for the three arks. Even as the world waits to see if the last-ditch Domino Deflection attempt will work, pandemonium still erupts...

Peter Mansfield is tasked with gathering the last group of people to leave the planet, the 'specials' who have ties to the space station that they don't yet know about. Mansfield has faced many difficult decisions over the years but will he survive long enough to make it to the station?

All three arks face serious danger and not every member of the Inner Circle will survive through the final days as Comet Clement approaches Earth for the moment of impact....



© 2015