Rosetta's comet mission discussion thread

[jerromyjon]

Someone could make a great tin-hat salesman!

(I actually have no idea what is going on with this. But it inspired my post. This is really weird. )

Well the jets are towards the sun, right? Perhaps the aliens are inside the sun transmitting the "start destruct sequence" signal which has to penetrate the exterior "decoy" layers. So now you know.

 

[OmCheeto]

Someone could make a great tin-hat salesman!

shhhhhhh! I've already alerted admin that I should not be a member of this forum. I think he thinks I was kidding...

Well the jets are towards the sun, right?

I don't know!

Perhaps the aliens are inside the sun transmitting the "start destruct sequence" signal which has to penetrate the exterior "decoy" layers. So now you know.

That could be.

But I just have so much fun thinking about all this stuff.

I consider the July 29th jet to be a case of fact being stranger than fiction.
Most likely, it is because I have nearly zero knowledge of chemistry.
Why was there a 7 fold increase in hydrogen sulphide? Could this jet have been caused by a thermally induced chemical reaction? Or was that just a freakishly deep pit, with stratified compounds?
I really have no idea.

But PF is filled with freakishly smart people, and I know they will answer, the silliest of questions.

------------------
And hopefully not ban me, for being an idiot.

 

[Dotini]

PF is filled with freakishly smart people, and I know they will answer, the silliest of questions.

Smart, yes, but also cautious and prudent. In the midst of rapid-fire discoveries, nobody wants to be caught saying anything that's seen to be wrong the very next week.

Seriously glad this is fun for you. Me too.

 

[jerromyjon]

Well the jets are towards the sun, right?

Looking at the shadows in the pictures I don't think it could be towards the sun. I was thinking about a comets "tail" being towards or away from the sun but now I forget which way it is. I have to say away since I think the tail tapers out at nearly the angle that a shadow would be cast. Sorry for not just googling it but I need to exercise my memory.

 

[OmCheeto]

Smart, yes, but also cautious and prudent. In the midst of rapid-fire discoveries, nobody wants to be caught saying anything that's seen to be wrong the very next week.

Sad. A thousand silly ideas might yield one good one.
It used to be called "brainstorming", in the olden days.

Do people ever do that anymore? Or have egos gotten so huge, that even the thought of positing an incorrect notion, sends people scurrying, like frightened mice?

Seriously glad this is fun for you. Me too.

 

[jerromyjon]

Do people ever do that anymore?

Now all I can run through my mind is this quote from Nugatory: "In order to broaden the horizons of science, you have to be standing at the frontier"

With that said, we are just sniffing the dust, saying is smells like hydrogen sulfide. I said that out loud earlier (I said "hydrogen sulfide?") and my wife just gave me a blank look and said "What?"... I imagine the greatest minds in the field are in heated conversations over this.

 

[OmCheeto]

Some of the descriptions in the article Dotini posted yesterday indicate that I have a lot to learn, as even the things they describe that they already know, make no sense to me.

Some highlights of things that may not be obvious if you read the article too fast:
1. The comet itself does not possesses its own magnetic field
2. The "diamagnetic cavity" is not a cavity inside the comet, it's a hole in the field that surrounds the comet.
3. That hole/cavity was created by the increased outgassing of the comet.The following excerpt from the article has me the most confused, so I may need to do some research.

...
The solar wind is the constant stream of electrically charged particles that flows out from the Sun, carrying its magnetic field out into the Solar System. Earlier measurements made by Rosetta and Philae had already shown that the comet is not magnetised, so the only source for the magnetic field measured around it is the solar wind.
...

[ref]
Specifically, the bolded portion.

Reading the wiki entry on "Interplanetary magnetic field", it's obvious that I've glossed over the fact that the solar wind, how do I put this, magnifies, is responsible for the sun's magnetic field being 100 times stronger at Earth's orbit, than if the wind did not exist.

I guess it's just hard for me to imagine how it works. But, apparently it does, and I should just shut up. But as most people know, I won't.

Also, looking at the moving GIF again, it looks as the though, from the shadows, that the gas jet was caused by that section rotating towards the sun.
Does anyone know how deep those pits get?
Has anyone counted all the pits? (I guess we could just count the jets)
Has anyone worked out the math on what effect the depth of the pits have on their thermal properties?
Is it possible to measure how much mass was lost from the one pit on July 29th, from the images?

Ok... I'll shut up now.

 

[OmCheeto]

Sad. A thousand silly ideas might yield one good one.
It used to be called "brainstorming", in the olden days.

Do people ever do that anymore? Or have egos gotten so huge, that even the thought of positing an incorrect notion, sends people scurrying, like frightened mice?

hmmm... This just came across my Facebook feed today. A very short interview with Freeman Dyson. One of the questions he answered, reminded me of this thread, and the spirit of PF.

http://scitation.aip.org/content/aip/magazine/physicstoday/news/10.1063/PT.5.3026 [physicstoday]
Jermey N. A. Matthews
12 August 2015
...
PT: Are you ever concerned that your contrarian view of climate science will become as much a part of your legacy as all the other contributions you’ve made to science? Or do you embrace that possibility?

DYSON: I do not care what my legacy will be. To me the most beautiful aspect of science is that it is a collaborative enterprise, with a multitude of people from all over the world taking part. In the long run, it does not matter who discovered what. We all share the joy of discovery even if we do not share the credit. I am happy to be skeptical about the prevailing dogma concerning climate change, whether or not it turns out that I am right. I can disagree vigorously with my colleagues and still remain friends.
...

--------------------
ps. My posts over the last two days should not be construed in any way that I am endorsing a loosening the rules against crackpottery. Thank you very much.

 

[jerromyjon]

My posts over the last two days should not be construed in any way that I am endorsing a loosening the rules against crackpottery.

There are plenty of less rigorous forums in which "crackpottery" runs rampant. I don't think any of us here at PF would enjoy that.

the solar wind, how do I put this, magnifies, is responsible for the sun's magnetic field being 100 times stronger at Earth's orbit, than if the wind did not exist.

Very interesting. Why have I never heard of this? Just when I think I have everything in perspective you throw me another curve ball.

 

[Dotini]

The song of Comet 67P — detected by the http://mashable.com/category/rosetta/ spacecraft last year — is actually caused by oscillations in the magnetic field surrounding the object, the European Space Agency (ESA) said in a blog post Wednesday.

http://mashable.com/2015/08/19/comet-song-rosetta/?utm_medium=feed&utm_source=feedburner&utm_campaign=Feed:+Mashablefrance+(Mashable!+Francais)
Rosetta's magnetometer started to detect the fluctuations when it got to Comet 67P in August 2014, ESA said. Until November, the spacecraft clocked about 3,000 instances of wave activity in the frequencies expected to make these sounds.

Radiation from the sun ionizes neutral particles spit out from the comet, and then those bits of material move perpendicular to the comet's induced magnetic field, ESA said. Scientists found that the current created from that movement is unstable, causing the oscillations that make the comet sing, the agency added.

http://www.ann-geophys.net/33/1031/2015/angeo-33-1031-2015.html
Abstract. We report on magnetic field measurements made in the innermost coma of 67P/Churyumov-Gerasimenko in its low-activity state. Quasi-coherent, large-amplitude (δ B/B ~ 1), compressional magnetic field oscillations at ~ 40 mHz dominate the immediate plasma environment of the nucleus. This differs from previously studied cometary interaction regions where waves at the cometary ion gyro-frequencies are the main feature. Thus classical pickup-ion-driven instabilities are unable to explain the observations. We propose a cross-field current instability associated with newborn cometary ion currents as a possible source mechanism.

 

[Dotini]

"Abundant molecular oxygen in the coma suggests that primordial O2 was incorporated into the nucleus during the comet’s formation...Current Solar System formation models do not predict conditions that would allow this to occur."
http://www.nature.com/nature/journal/v526/n7575/full/nature15707.html'In looking at exo-planets, "the combination of O2 and methane has been taken as a sign that you might have life underneath," she said.

"On this comet we have both, but we don't have life. So having oxygen may not be a very good bio-signature."'
http://news.yahoo.com/discovery-oxygen-comet-big-surprise-181858811.html

 

[Dotini]

"Here we report observations of water ice on the surface of comet 67P/Churyumov–Gerasimenko, appearing and disappearing in a cyclic pattern that follows local illumination conditions, providing a source of localized activity. This water cycle appears to be an important process in the evolution of the comet, leading to cyclical modification of the relative abundance of water ice on its surface."

http://www.nature.com/nature/journal/v525/n7570/full/nature14869.html

 

[Dotini]

Various scenarios of radiolysis are discussed as the origin of molecular oxygen in the comet.
http://blogs.esa.int/rosetta/2015/10/28/first-detection-of-molecular-oxygen-at-a-comet/

High-resolution measurements allowed molecular oxygen (O2) to be distinguished from other species like sulphur (S) and methanol (CH3OH). The detection of the coma gases is stronger closer to the comet nucleus, as expected. The contribution to the detection from contamination from the spacecraft thruster firings during manoeuvres is very low. Data from A. Bieler et al. (2015)

The strong correlation of molecular oxygen abundance with water vapour indicates a shared origin and release mechanism from the nucleus. Data from A. Bieler et al. (2015)

The O2/H2O ratio does not vary significantly over the study period. Short-lived strong variations are attributed to the decrease of the O2 ratio for occasionally higher H2O abundances linked to the daily water-ice cycle. The overall consistent level implies that O2 is not produced today by solar wind or UV interaction with surface ices, otherwise it would rapidly decrease due to the comet's increased activity. Instead the O2 must have been incorporated into the comet's ices during its formation in the early Solar System, and is being released with the water vapour today. Data by A. Bieler et al. (2015)

------------------------

“Regardless of how it was made, the O2 was also somehow protected during the accretion stage of the comet: this must have happened gently to avoid the O2 being destroyed by further chemical reactions,” adds Kathrin.

 

[OmCheeto]

SciAm wouldn't lie to us, would they?

Historic Rosetta Mission to End with Crash into Comet
There were other options, but super close-up shots on descent will provide science bonanza
By Elizabeth Gibney and Nature magazine | November 4, 2015

A year since a probe called Philae made history by touching down on a comet, the team that pulled off the feat is plotting a different kind of landing. Next September, the European Space Agency will crash Philae’s mothership Rosetta into the icy dust ball, but as gently as possible.
...

 

[Imager]

The FAQ on the ESA website says 12 year mission. Although it doesn't look like the FAQ has been updated recently.

How long will the Rosetta spacecraft operate?
Rosetta’s planned lifetime is about 12 years. The nominal mission ends in December 2015, after the comet reaches its closest point to the Sun (in August 2015) and starts heading back towards the outer Solar System.
http://www.esa.int/Our_Activities/Space_Science/Rosetta/Frequently_asked_questions

November 12, 2015, one year aniversary of Philae's landing, did anyone bake a cake?

 

[Imager]

Sadly, only a couple months remaining for Rosetta, but a big Cheer for the ESA! Job well done!

from Rueters:

The European spacecraft Rosetta will crash-land on the surface of the comet 67P/Churyumov-Gerasimenko and end its 12-year space odyssey on Sept. 30, France's National Centre for Space Studies (CNES) said on Thursday.

 

[1oldman2]

Sad to see the mission end, but what a way to go. Congratulations ESA!

 

[1oldman2]

End of the line today. http://blogs.esa.int/rosetta/2016/07/26/farewell-silent-philae/
Tomorrow, 27 July 2016 at 09:00 UTC / 11:00 CEST, the Electrical Support System Processor Unit
(ESS) on Rosetta will be switched off. The ESS is the interface used for communications between
Rosetta and the lander, Philae, which has remained silent since 9 July 2015.

 

[1oldman2]

It seems the final curtain call is coming up. From, http://www.planetary.org/blogs/emily-lakdawalla/2016/0726-rosetta-end-of-mission-plans.html
"Last week, ESA announced when and where Rosetta is going to touch down, bringing the
mission to an end: within the Ma'at region on the comet's head, at approximately 10:30 UTC
(12:30 CEST / 06:30 EDT / 03:30 PDT) on September 30. It took me a while to figure out its
position relative to the Philae landing locations -- comet geography is challenging! -- but I think this is how they all relate to each other"

 

[Borg]

Philae lander has finally been found.

Philae is seen wedged against a large over-hang. Its 1m-wide box shape and legs are unmistakable, however.
Rosetta had previously surveyed this location - dubbed Abydos - without success.
The difference now is a closer-in perspective and a change in the seasons on the comet, which means the hiding place has become properly illuminated.

Laying on its side with one leg sticking up:

 

[Jonathan Scott]

From information on the ESA site, the top right picture is an earlier wider angle image of the comet's "head" with a red dot to show the approximate location of Philae.

 

[1oldman2]

Micro-gravity landings can be rough!
http://www.space.com/27767-philae-comet-landing-nearly-failed-infographic.html

The action took place 317 million miles (510 million kilometers) from Earth
and 14 miles (22.5 km) from the comet, Rosetta released the lander. Philae
fell towards the comet for seven hours.

Philae hit the surface at 3.3 feet per second (1 meter per second). Harpoons
and a rocket meant to secure the probe to the comet, failed to fire.

In its first bounce, Philae traveled about 0.6 miles (1 km) up and an equal
distance across the comet. Philae ascended with a speed of 15 inches (38
centimeters) per second. Escape velocity from the comet is 19.7 inches (50
cm) per second.

After a second bounce lasting about seven minutes, Philae finally came to
rest on the surface.

 

[OmCheeto]

...

Philae hit the surface at 3.3 feet per second (1 meter per second).

Those speeds didn't really mean anything to me, so I googled them.
They are about 50% slower than an average human's walking speed.

And it made me lol when thinking about walking into a wall, and bouncing back 1/2 a mile, or 1 km.

Exophysics* is funny.
At least, for me, anyways

*Yah, I know... But you know what I mean.

 

[1oldman2]

http://www.planetary.org/blogs/emily-lakdawalla/2016/09091029-rosetta-end-of-mission-update.html

The European Space Agency posted several articles this morning about the plans for the end of the Rosetta mission
scheduled for September 30, just three weeks from now. On September 29, a rocket burn will essentially cancel out
Rosetta's orbital motion around the comet, initiating a free fall from an altitude of 20 kilometers. The spacecraft
will impact the comet at a speed of about 90 centimeters per second at 04:20 PDT / 07:20 EDT / 11:20 UTC / 13:20 CEST, give or take 20 minutes. Upon impact, the spacecraft will automatically "passivate," cutting the radio connection to Earth and ending the mission forever.

http://www.esa.int/Our_Activities/S...setta_s_descent_towards_region_of_active_pits
9 September 2016
Squeezing out unique scientific observations until the very end, Rosetta’s
thrilling mission will culminate with a descent on 30 September towards a
region of active pits on the comet’s ‘head’.

The region, known as Ma’at, lies on the smaller of the two lobes of Comet 67P
/Churyumov-Gerasimenko. It is home to several active pits more than 100 m in
diameter and 50-60 m in depth - where a number of the comet’s dust jets originate.

 

[1oldman2]

Here are links to the live stream, I'm hoping its more than just talking heads, would be great to get video of the approach.
Rosetta - 3:15am to 5:00am EDT 9/30
http://www.ustream.tv/nasajpl2
http://www.nasa.gov/multimedia/nasatv/index.html#public

 

[Jonathan Scott]

Nice HHGTTG reference in one of the last tweets:
"What’s this thing coming towards me…I wonder if it will be friends with me?!"

 

[harrylin]

Summary with last pictures here:
http://www.esa.int/Our_Activities/S...tta_s_journey_ends_in_daring_descent_to_comet

 

[enorbet]

Last night I watched an unusually good film (German made with English soundtrack) recently added on Amazon Prime, called The Rosetta Mission.. It does cover some nicely technical issues not commonly seen on film and covers more than just Rosetta. For example it goes into some detail on just how long it takes and how expensive it can be to develop a trustworthy craft. A friend of mine works at Goddard Space Flight center who has a job reducing noise and sussing out ground loops so it was great seeing some time spent on how circuitry is crafted and developed, and why it must be obsolete before it's even launched. Reliability trumps all. Those fellows deserve deep recognition. There was also an in-depth look at specialized insulating materials for handling extreme heat and cold and the sort of testing required for deep confidence.

All in all, I recommend this film to any interested in a more technical view than is commonly produced about Space Exploration.

 

[enorbet]

Nice HHGTTG reference in one of the last tweets:
"What’s this thing coming towards me…I wonder if it will be friends with me?!"

That whale clearly forgot to bring a towel. ;)

 

[1oldman2]

The really cool thing about these types of missions is they just keep giving.

http://www.astrowatch.net/2016/10/astronomers-predict-possible-birthplace.html

When the Rosetta spacecraft successfully touched down on comet 67P/Churyumov-Gerasimenko on September 30, 2016, the news was shared globally via Twitter in dozens of languages. Citizens the world over were engaged by the astronomical achievement, and now the European Space Agency and NASA are eager to learn as much as possible about the critically important celestial body of ice.

Using statistical analysis and scientific computing, astronomers at Western University have charted a path that most likely pinpoints the very origins of comet 67P/Churyumov-Gerasimenko, which is vital information in discovering what kind of material it is made from and just how long it has been present in our solar system.

Mattia Galiazzo, a postdoctoral fellow in Western’s Department of Physics & Astronomy, presented his findings today at the joint 48th annual meeting of the Division for Planetary Sciences (DPS) of the American Astronomical Society (AAS) and 11th annual European Planetary Science Congress (EPSC) in Pasadena, California. Galiazzo collaborated on the findings with solar system expert Paul Wiegert from Western’s Centre for Planetary Science & Space Exploration.

"These results come from computations of the comet’s orbit from the present to the past, which is computationally difficult due to the chaosity of the orbit caused by close encounters with Jupiter," says Galiazzo. "Thus the details are obscure but we can establish a dynamical pathway from its current orbit back to the Kuiper belt."

Galiazzo and Wiegert think that 67P/Churyumov-Gerasimenko is relatively new to the inner parts of our solar system, having only arrived about 10,000 years ago. Prior to this time, the comet would have been inactive in frozen storage far from the Sun.

Previous studies show that similar comets - known as Jupiter Family comets - historically stay in the inner parts of our solar system for 12,000 years, therefore recognizing comet 67P/Churyumov-Gerasimenko as a member of the Jupiter Family makes sense.

The majority of the Jupiter Family comets are thought to come from the Kuiper belt - a ring-shaped accumulation of comets, asteroids and other space bodies in the solar system beyond the known planets - and Galiazzo and Wiegert believe, based on initial analysis of their investigation, that this is the case for 67P/Churyumov-Gerasimenko, as well.

Their analysis shows that, in transit, the comet likely spent millions of years in the scattering disk, a distant portion of the Kuiper belt, at about twice the distance of Neptune - our solar system’s most distant planet. This distant origin for 67P/Churyumov-Gerasimenko implies it would be made from primordial material, meaning minerals that existed in their current form since before Earth was formed.

 

[1oldman2]

A very good piece.
http://www.planetary.org/blogs/guest-blogs/2016/1107-rosetta-in-the-rearview.html

"For years, planetary scientists have conceived of comets as the dirty snowballs of the solar system, largely made of ices but with a dusty coating that dulls their reflectivity, making them appear dark in observations. However, the OSIRIS camera team determined that the comet has a density of just 470 kilograms per cubic meter, less than half the density of water ice. The comet must be very porous, with lots of free space inside. You would think that the low density also implies an ice-rich (rather than dust-rich) comet, but OSIRIS found very few exposed water ice patches on the surface. A high porosity, near 70%, would permit a denser mixture with more dust and less ice and explain the lack of water ice patches and the density. Rather than a ball of ice covered in dust, it seems that comets are a mixture of the two: An icy dirtball may be a better description rather than a dirty snowball."

And more.
http://www.astrowatch.net/2016/11/avalanches-not-internal-pressure-cause.html