Mars moon got its grooves from rolling stones, study suggests

November 20, 2018, Brown University
Much of Phobos' surface is covered with strange linear grooves. New research bolsters that idea the boulders blasted free from Stickney crater (the large depression on the right) carved those iconic grooves. Credit: NASA/JPL-Caltech/University of Arizona

A new study bolsters the idea that strange grooves crisscrossing the surface of the Martian moon Phobos were made by rolling boulders blasted free from an ancient asteroid impact.

The research, published in Planetary and Space Science, uses computer models to simulate the movement of debris from Stickney crater, a huge gash on one end of Phobos' oblong body. The models show that boulders rolling across the surface in the aftermath of the Stickney impact could have created the puzzling patterns of grooves seen on Phobos today.

"These grooves are a distinctive feature of Phobos, and how they formed has been debated by for 40 years," said Ken Ramsley, a planetary science researcher at Brown University who led the work. "We think this study is another step toward zeroing in on an explanation."

Phobos' grooves, which are visible across most of the moon's surface, were first glimpsed in the 1970s by NASA's Mariner and Viking missions. Over the years, there has been no shortage of explanations put forward for how they formed. Some scientists have posited that large impacts on Mars have showered the nearby moon with groove-carving debris. Others think that Mars' gravity is slowly tearing Phobos apart, and the grooves are signs of structural failure.

Still other researchers have made the case that there's a connection between the grooves and the Stickney impact. In the late 1970s, planetary scientists Lionel Wilson and Jim Head proposed the idea that ejecta—bouncing, sliding and rolling boulders—from Stickney may have carved the grooves. Head, a professor in Brown's department of Earth, Environmental and Planetary Sciences, was also a coauthor of this new paper.

For a moon the size of the diminutive Phobos (27 kilometers across at its widest point), Stickney is a huge crater at 9 kilometers across. The impact that formed it would have blown free tons of giant rocks, making the rolling boulder idea entirely plausible, Ramsley says. But there are also some problems with the idea.

Researchers used computer models to trace the possible path of boulders ejected from Stickney crater on Mars' moon Phobos. The simulations showed that boulders could have carved the iconic grooves seen on Phobos' surface. Credit: Ken Ramsley / Brown University

For example, not all of the grooves are aligned radially from Stickney as one might intuitively expect if Stickney ejecta did the carving. And some grooves are superposed on top of each other, which suggests some must have already been there when superposed ones were created. How could there be grooves created at two different times from one single event? What's more, a few grooves run through Stickney itself, suggesting that the crater must already have been there when the grooves formed. There's also a conspicuous dead spot on Phobos where there are no grooves at all. Why would all those rolling boulders just skip one particular area?

To explore those questions, Ramsley designed computer models to see if there was any chance that the "rolling boulder model" could recreate these confounding patterns. The models simulate the paths of the boulders ejected from Stickney, taking into account Phobos' shape and topography, as well as its gravitational environment, rotation and orbit around Mars.

Ramsley said he had no expectations for what the models might show. He wound up being surprised at how well the model recreated the groove patterns seen on Phobos.

"The model is really just an experiment we run on a laptop," Ramsley said. "We put all the basic ingredients in, then we press the button and we see what happens."

The models showed that the boulders tended to align themselves in sets of parallel paths, which jibes with the sets of parallel grooves seen on Phobos. The models also provide a potential explanation for some of the other more puzzling groove patterns.

The simulations show that because of Phobos' small size and relatively weak gravity, Stickney stones just keep on rolling, rather than stopping after a kilometer or so like they might on a larger body. In fact, some boulders would have rolled and bounded their way all the way around the tiny moon. That circumnavigation could explain why some grooves aren't radially aligned to the crater. Boulders that start out rolling across the eastern hemisphere of Phobos produce grooves that appear to be misaligned from the crater when they reach the western hemisphere.

Mars moon got its grooves from rolling stones, study suggests
Researchers used computer models to simulate the path of ejecta from Stickney crater on Mars' moon Phobos. The simulations show how boulders take a flying leap over one particular area of Phobos, explaining why it's devoid of grooves. Credit: Ken Ramsley / Brown University

That round-the-globe rolling also explains how some grooves are superposed on top of others. The models show that grooves laid down right after the impact were crossed minutes to hours later by boulders completing their global journeys. In some cases, those globetrotting boulders rolled all the back to where they started—Stickney crater. That explains why Stickney itself has grooves.

Then there's the dead spot where there are no grooves at all. That area turns out to be a fairly low-elevation area on Phobos surrounded by a higher-elevation lip, Ramsley says. The simulations showed that boulders hit that lip and take a flying leap over the dead spot, before coming down again on the other side.

"It's like a ski jump," Ramsley said. "The boulders keep going but suddenly there's no ground under them. They end up doing this suborbital flight over this zone."

All told, Ramsley says, the models answer some key questions about how ejecta from Stickney could have been responsible for Phobos' complicated groove patterns.

"We think this makes a pretty strong case that it was this rolling boulder accounts for most if not all the grooves on Phobos," Ramsley said.

Explore further: Fantastic Phobos

More information: Kenneth R. Ramsley et al, Origin of Phobos grooves: Testing the Stickney Crater ejecta model, Planetary and Space Science (2018). DOI: 10.1016/j.pss.2018.11.004

Related Stories

Fantastic Phobos

August 21, 2012

(Phys.org) -- Some 135 years after its discovery, Mars’ largest moon Phobos is seen in fantastic detail – and in 3D – in an image taken by ESA’s Mars Express spacecraft as it passed just 100 km by.

How this Martian moon became the 'Death Star'

October 12, 2016

Mars' largest moon, Phobos, has captured public imagination and been shrouded in mystery for decades. But numerical simulations recently conducted at Lawrence Livermore National Laboratory (LLNL) have shed some light on the ...

Mars' moon Phobos is slowly falling apart

November 10, 2015

The long, shallow grooves lining the surface of Phobos are likely early signs of the structural failure that will ultimately destroy this moon of Mars.

Recommended for you

Periodic radio signal detected from the blazar J1043+2408

December 12, 2018

Using Owens Valley Radio Observatory (OVRO), astronomers have detected a periodic signal in the radio light curve of the blazar J1043+2408, which could be helpful in improving our understanding about the nature of blazars ...

InSight Mars lander takes its first selfie

December 12, 2018

NASA's InSight lander isn't camera-shy. The spacecraft used a camera on its robotic arm to take its first selfie—a mosaic made up of 11 images. This is the same imaging process used by NASA's Curiosity rover mission, in ...

38 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

Solon
1.3 / 5 (14) Nov 20, 2018
What a joke, another laughable plasma ignoramus this Ramsley.
SkyLight
5 / 5 (13) Nov 20, 2018
Solon's remark translated to scientific English:

This Ramsley guy is yet another in a long line of scientists who steadfastly refuse to consider the idiotic and baseless notion that such grooves are created by humungous electrical discharges from some unexplained, and unexplainable, mysterious Flying Death Battery From Outer Space.

Well, full marks to Ramsey and his team for coming up with a workable idea to possibly explain the grooves: food for thought.
rrwillsj
3.7 / 5 (3) Nov 20, 2018
How disappointing!
No thundermugs tossed by drunken deities littering the Phobos landscape.
Captain Stumpy
4.6 / 5 (9) Nov 20, 2018
@solon trolling for the eu cult
What a joke, another laughable plasma ignoramus this Ramsley.
obviously not considering he studied engineering... or did you miss that?
Engineering Adviser / Instructor
not only was he an engineer for a decade, but he's also directly connected to several sattelites in orbit as well as teaching
spacecraft and commercial product design
you really should do some basic homework before opening your mouth and looking like a complete idiot

more to the point: if an *engineer* says it aint electric woo, it really aint electric woo
rrwillsj
1 / 5 (2) Nov 20, 2018
Yeah, an engineer who confuses the electric with the woo? BBQ!

Electric reality will beat the woo everyday!
cantdrive85
1.5 / 5 (8) Nov 20, 2018
"These grooves are a distinctive feature of Phobos, and how they formed has been debated by planetary scientists for 40 years,"

And nary a valid nor viable explanation has been put forth by the plasma ignoramuses in those forty odd years. Rolling stones? Flying boulders! The ridiculousness one will invoke to resist a simple concept is monumental, apparently.
"We put all the basic ingredients in, then we press the button and we see what happens."

Right, computer games.
BTW, where are these flying boulders? Are they dark boulders?
cantdrive85
2.1 / 5 (7) Nov 20, 2018
Rollin' Stone.......

https://youtu.be/9AH5J2zQHqc
Surveillance_Egg_Unit
1.7 / 5 (6) Nov 20, 2018
https://www.youtu...96uKZ7yQ

Rollling' Stones ha ha ha ha ha

Won't get fooled again

jonesdave
4.2 / 5 (10) Nov 21, 2018
And nary a valid nor viable explanation has been put forth by the plasma ignoramuses in those forty odd years. Rolling stones? Flying boulders! The ridiculousness one will invoke to resist a simple concept is monumental, apparently.


Says an ignorant mug who has no valid hypothesis for this at all. All talk, no science.
cantdrive85
1.5 / 5 (8) Nov 21, 2018
Says an ignorant mug who has no valid hypothesis for this at all. All talk, no science.

Wrong as usual, the same processes that is occurring on Io, Enceladus, and which creates cometary jets. Electric discharge is a simple and obvious mechanism to create all of the observed features. Now invisible boulders required.
jonesdave
4.1 / 5 (9) Nov 21, 2018
Says an ignorant mug who has no valid hypothesis for this at all. All talk, no science.

Wrong as usual, the same processes that is occurring on Io, Enceladus, and which creates cometary jets. Electric discharge is a simple and obvious mechanism to create all of the observed features. Now invisible boulders required.


Lol. Io is volcanism, Enceladus is cryovalcanism, and comet jets are from sublimating volatiles, entraining dust and ice. As proven.
jonesdave
4.2 / 5 (10) Nov 21, 2018
No invisible boulders required.


Just invisible, impossible electric woo.
cantdrive85
2 / 5 (8) Nov 21, 2018
So you acknowledge the conditions required for this electric "woo", yet claim it is impossible? You are one confused moronic puppy jonesdumb.
jonesdave
4.1 / 5 (9) Nov 21, 2018
So you acknowledge the conditions required for this electric "woo", yet claim it is impossible? You are one confused moronic puppy jonesdumb.


I did no such thing. As I said, 'impossible'.
jonesdave
4.1 / 5 (9) Nov 21, 2018
Just for the hard of thinking; the Rosetta mission finished just over two years ago. That spacecraft had a whole suite of instruments, and was in close proximity to a comet for around two years. Not a single peep out of the magnetometer to show these imaginary discharges. On the other hand, the jets at 67P, and other comets have been studied. They are gas and dust and, sometimes, ice. The spectrum is that of sunlight reflected from dust. There was no electrical woo, there was no rock. The electric comet was a busted flush long before this mission ended. One would have thought that its proponents would have throw in the towel after the Tempel 1 impact results came out. Ice, gas and dust, and a crater too large to have been made in rock. The electric comet woo requires rock, because the loons who made it up think comets were blasted off of rocky planets by giant lightning bolts! I mean, what's not to believe? Lol.
cantdrive85
1.8 / 5 (5) Nov 21, 2018
You acknowledge surface charging due to interaction with SW, this is all that is required for electrostatic discharge. Put this object near another charged object and there will be an electric discharge. Just like what happened to Cassini.
http://sci.esa.in...on-beam/
The only thing that is impossible jonesdumb is your ability to think and reason.
cantdrive85
2.3 / 5 (3) Nov 21, 2018
Not a single peep out of the magnetometer to show these imaginary discharges.

Already pointed to the measured outburst that was too energetic for your faerie tales, no memory of that?
cantdrive85
2.3 / 5 (3) Nov 21, 2018
The electric comet woo requires rock,

Which would be too hard to drill into with Philae's SD2 equipment. And what do ya know, that is exactly what happened.
fourinfinities
5 / 5 (5) Nov 21, 2018
If Phobos grooved to the rolling stones, that just shows its age...
jonesdave
3.7 / 5 (6) Nov 21, 2018
You acknowledge surface charging due to interaction with SW, this is all that is required for electrostatic discharge. Put this object near another charged object and there will be an electric discharge.


No, it won't, and no it didn't. No electric discharges of any kind. And surface charging essentially disappears when the solar wind stop reaching the nucleus. Which just happens to coincide with the time when the comet is most active.
jonesdave
3.7 / 5 (6) Nov 21, 2018
Already pointed to the measured outburst that was too energetic for your faerie tales, no memory of that?


And which had nothing to do with any electric woo! Lol. Likely a subsurface build up of pressure, as the authors say. There was ice in that outburst! And nothing in the mag data. Only an idiot would think that the outburst was anything to do with electric woo.

jonesdave
3.7 / 5 (6) Nov 21, 2018
The electric comet woo requires rock,

Which would be too hard to drill into with Philae's SD2 equipment. And what do ya know, that is exactly what happened.


Drilling wasn't attempted. They hammered on it. And the velocity of the sound waves from that hammering was measured, and the properties and strength of the surface estimated from it. Neither of those properties were anything like rock. Not even close. And they sent radio waves through the whole of one of the lobes. Again, nothing like rock. They also tested the electrical permittivity of the surface. Guess what? Nothing like rock. Both MIRO and Philae tested the thermal inertia of the surface and near-surface. Nothing like rock. The density of the comet was measured by the RSI experiment, as well as the behaviour of the spacecraft when in bound orbits. Nothing like rock.

tl;dr? There was no rock.
jonesdave
3.7 / 5 (6) Nov 21, 2018
Drilling wasn't attempted.


Correction; it was. They had one attempt. It seems to have been unsuccessful due not to the hardness of the surface, but by drilling into vacuum! The strange orientation of the craft meant that the drill could never have reached the surface.

Planning and implementation of the on-comet operations of the instrument SD2 onboard the lander Philae of Rosetta mission
Di Lizia, P. et al.
https://core.ac.u...3150.pdf
terne57
1 / 5 (1) Nov 21, 2018
Looks like re-entry burn on the front of that big rock, and the lines look like burning and melting of that big rock, just saying.
rrwillsj
not rated yet Nov 21, 2018
Well, my explanation for the "why" of the electric woo loons? Is the kid who kept taking the lightbulb out of thee lamp socket. Then sticking his tongue into the empty socket until he got a shock. Repeatedly.

Yep, that explains their ridiculous assertions of gibbering negative evidence.

Of that I am currently positive.
rrwillsj
not rated yet Nov 21, 2018
uhh, terme. In order for your comment to make any sense? Phobos would presently be located on the Martian surface.

In case no one has explained it to you? Phobos is presently in orbit around Mars.

You could actually prove that to yourself with a modest telescope.

I apologize that you will fail to see lightning bolts flashing off it.

Try to bear up under your disappointment.

Come to think of it, Consuming kegs of "beer up' might assist you in visualizing those invisible lightning bolts?

Make sure you have a thundermug handy for the inevitable results of "renting" the brew.
granville583762
3 / 5 (4) Nov 21, 2018
Phobos
a martian mystery
parallel meteor tracks
rolling and bouncing as though on tram lines
on opposing sides of the craters
where old worn tracks
are over run with fresh tracks
running in the same parallel groves
where even the explosive rock fragments
from each meteor impact follow the same grove
certainly a mystery worthy of a Phobos landing
almost as though the martians have jumped ship
now living in the Phobos craters
creating these linear parellel grooves
for some strange ritual rites
martian witch craft is a foot
as when phobos is full in the martian sky
when the martian polar lights doth flicker
and phobos light in full moon
light the ancient martian landscape
that in ancient times
was a myriad of ancient martian rites
as phobos is only a shadow
that mars once was
as all that we now see on phobos
is kept a new by the surviving ancient witch's
as now mars is just an ancient barren landscape
under the light of phobos moon light
Mark Thomas
not rated yet Nov 22, 2018
My post in 2016:

https://phys.org/...bos.html

Mark's Groovy Theory (hypothesis)

After a large, off-center impact formed Stickney Crater, Phobos received enough angular momentum (was spinning fast enough) that the secondary ejecta (mostly rocks ejected from Stickney Crater) created PARALLEL (not radial) grooves and chains of pits as those rocks rolled and bounced over and through the rotating surface of Phobos.

Key facts: 1. the escape velocity of Phobos is only ~25 mph, so Phobos would not have to spin very fast; 2. Stickney is a very large crater relative to Phobos, and the primary impactor could have imparted significant angular momentum; 3. statistically, an off-center impact is the most likely scenario; 4. this results in parallel grooves at all latitudes, as we see on Phobos, which is hard to achieve otherwise; and 5. there appear to be a few radial grooves that turned into parallel grooves . . .
Captain Stumpy
5 / 5 (1) Nov 22, 2018
@cantcomprehendscience the eu cult loon
Already pointed to the measured outburst that was too energetic for your faerie tales
you stated Cassini would need to be put in safe-mode to protect it from a highly energetic plasma discharge - and your prediction tanked

moreover, your own link above to ESA Science proves you're an idiot with your own claims about MS not knowing plasma physics - it stated: "but evidence of surface charging on other objects in the Solar System has been elusive". so it's known and it's predicted by MS (says so in the first paragraph in bold)

that quoted statement proves that they've been looking for it

the article also indicates it's nowhere near the levels capable of the geological formations you're claiming

*and* it's already known to have limited effects on dust (Eros and Saturnian moons, etc)

the article you linked debunks most of your idiot eu claims on this site
granville583762
5 / 5 (2) Nov 22, 2018
Wiccan Phobos

Phobos is an average 22km diameter
If these grooves are to do with Phobos spin
any 22km diameter moon's meteor impact craters have the same groves
Phobos gravity is 0.0057 m/s2
so how did gravity provide sufficient weight to force the meteor fragments into Phobos
These grooves are pretty deep
if you stood on Phobos
unless you were chained down you would simply float away
any meteor capable of making impact craters this deep in Phobos
would shatter equidistant in all directions and the rock fragments rebound in all directions back into the vacuum
We come back to Wiccan Phobos
There's witch craft in these Phobos grooves
jonesdave
3 / 5 (2) Nov 22, 2018
TBH the thundercult cannot rely on electrostatic charging to explain things at comets. According to them comets are "just asteroids on elliptical orbits." Leaving aside the fact that there are shed loads of asteroids on elliptical orbits that don't outgas, asteroids are permanently subjected to the solar wind. which causes the highest charges. The sunlit side will go a few volts + due to photoemission. This happens to both asteroids and comets. The largest charge comes from the higher mobility of electrons in the solar wind (larger gyroradius), meaning they have access to the dark side of the body. This means that the unlit side can charge up negatively to fairly high values. This could cause some dust movement near the terminator. This effect has long been proposed for the Moon.
Of course, the solar wind is getting nowhere near a comet when it is most active, but continually impacts asteroid surfaces.
jonesdave
3.7 / 5 (3) Nov 22, 2018
An interesting paper re the above post;

Grid-free 2D plasma simulations of the complex interaction between the solar wind and small, near-Earth asteroids
Zimmerman, M. I. et al.
https://ntrs.nasa...1018.pdf

And, for the case of comets;

Surface charging and electrostatic dust acceleration at the nucleus of comet 67P during periods of low activity
Nordheim, T. A. et al.
https://www.scien...1500238X
granville583762
5 / 5 (2) Nov 23, 2018
Sparking Clogs
space.com> Phobos orbits close to Mars since it has no atmosphere and no magnetosphere it plows through streams of solar wind and absorbs the electrically charged particles on its dayside. This, in turn, leaves a void over its nightside. As a result, negatively charged electrons from the solar wind fill this void and statically charge the moon's nightside.
https://www.space...bos.html
solar wind negatively charges the earth's moon craters as the ions flow past charging up the region in shadow
shadow charging reach's 10,000volts
astronauts staged on Phobos can charge their suits and go round all the electrical equipment like a lightning conductor
if the martians get this voltage on the move Phobos could have a magnetic field
10,000volts miles from anywhere has some useful possibilities
could be a useful electricity supply
Concerning sparking clogs
Up north in Manchester they still wear clogs
Solon
not rated yet Nov 23, 2018
An interesting paper re the above post;

Grid-free 2D plasma simulations of the complex interaction between the solar wind and small, near-Earth asteroids
Zimmerman, M. I. et al.
https://ntrs.nasa...1018.pdf
And, for the case of comets;

Surface charging and electrostatic dust acceleration at the nucleus of comet 67P during periods of low activity
Nordheim, T. A. et al.
https://www.scien...1500238X


Good finds JD, I'll post those links on the TB site.
jonesdave
3 / 5 (2) Nov 23, 2018
An interesting paper re the above post;

Grid-free 2D plasma simulations of the complex interaction between the solar wind and small, near-Earth asteroids
Zimmerman, M. I. et al.
https://ntrs.nasa...1018.pdf


Good finds JD, I'll post those links on the TB site.


Pointless. They wouldn't understand them and/ or would misinterpret them! You can go back much further if you like, before the EU cult even existed, to this;

On the electrostatic charging of the cometary nucleus
Mendis, D. A. et al (1981)
http://adsabs.har...49..787M
rrwillsj
not rated yet Nov 23, 2018
I can understand the deities bowling balls bouncing down the lanes of the Phobos bowling alley. And flying off into Space to bang around the theosophist flying saucers.

However, what I do not understand. If the EU loons are correct? Hahahaha... uhhm.

If in somr mystical fairieland the EU cultist loons were correct? Then all those beer cans the deities left littering Phobos should be magnetically stuck to the floor!
jonesdave
3 / 5 (2) Nov 23, 2018
Good finds JD, I'll post those links on the TB site.


Perhaps you could post this as well;

Detection of Water Vapor in Halley's Comet
Mumma, M. J. et al (1986)
http://science.sc...757/1523

And then ask the few remaining denizens of woo central why they think Thornhill was lying to them 20 years after that paper, and many others in the intervening period, which definitively detected H2O at comets. He was still telling them that it was OH! Talbott was a co-author of that execrable electric comet poster - perhaps he can explain?

But a much different vantage point on the water question is possible. When astronomers view the comas of comets spectroscopically, what they actually see is the hydroxyl radical (OH), which they assume to be a residue of water (H2O) broken down by the ultraviolet light of the Sun (photolysis).


2006.

Can't be nice when your high priests lie to you, I imagine.

rrwillsj
5 / 5 (1) Nov 24, 2018
Oh but jd, that's the high priest's job! To lie to their patients. Oops, silly me. I meant faithful worshipers. Yes, yes I did.

goddess I'm an awful human being!

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.