APOD: Galileo's Europa Remastered (2014 Nov 27)

[APOD Robot]

Galileo's Europa Remastered

Explanation: Looping through the Jovian system in the late 1990s, the Galileo spacecraft recorded stunning views of Europa and uncovered evidence that the moon's icy surface likely hides a deep, global ocean. Galileo's Europa image data has been newly remastered here, using improved new calibrations to produce a color image approximating what the human eye might see. Europa's long curving fractures hint at the subsurface liquid water. The tidal flexing the large moon experiences in its elliptical orbit around Jupiter supplies the energy to keep the ocean liquid. But more tantalizing is the possibility that even in the absence of sunlight that process could also supply the energy to support life, making Europa one of the best places to look for life beyond Earth. What kind of life could thrive in a deep, dark, subsurface ocean? Consider planet Earth's own extreme shrimp.

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[bystander]

http://asterisk.apod.com/viewtopic.php?t=34141

[Ann]

It's good to see NASA do new things with old images!

Europa is my second favorite Solar system moon, second only after Luna, with Enceladus coming in a close third. Titan is only number four in my book. I'm less fascinated by Titan than most people, because that moon is so forbiddingly cold.

But it's hard not to compare Europa with Titan when I look at today's "remastered" image of the Jovian moon. The orange color of the extremely numerous cracks on the surface strikes me as pretty much exactly the same color as the atmosphere of Titan. They color would be due to exactly the same thing, the presence of organic components.

There are a number of extremely big differences between Europa and Titan. Titan has a most remarkably thick atmosphere, while Europa has no (substantial) atmosphere at all. On Europa, the matter containing organic compounds likely originate from below the surface, and they reach the surface through cracks in the ice. So Europa is either liquid or at least "soft" below its surface. We have also every reason to believe that this soft subsurface material is predominantly made of water ice. On Titans, the icy surface is so cold that it is every bit as hard as rock. There are some signs of cryovolcanism on Titan, suggesting that softer material is coming up from below, but the evidence so far is indirect. So we have moderately good reasons to believe that there are organic compounds mixed with liquid water inside Europa, while we have no really good reasons, so far, to assume that there are organic compounds mixed with liquid water or soft ice on or inside Titan.

Ann

[Boomer12k]

Somebody got Europa all scratched....

:---[===] *

[Guest]

I noted some 'pink' areas in the image near the upper limit of the 11 to 12 o'clock range. Is this an artifact caused by processing/raw data variance. or is that an actual difference in surface makeup in those areas? Any ideas? I didn't see any evidence of 'recent' activity or impacts...

[Chris Peterson]

I noted some 'pink' areas in the image near the upper limit of the 11 to 12 o'clock range. Is this an artifact caused by processing/raw data variance. or is that an actual difference in surface makeup in those areas? Any ideas? I didn't see any evidence of 'recent' activity or impacts...

It doesn't appear to be an artifact. So I think it represents something different about the surface there- either different material (or more likely) a different mix of material.

[Bellerophon]

One of the things I like about this image is that it isn't what I expected. I was bracing myself for a picture of the Turkey Nebula, which of course would bear no resemblance to a turkey.
Happy Thanksgiving!

[Buddy]

My guess is that all potentially habital bodies will have life. "Life" being bacterial or similar organisms, which is what 99+% of scientists mean. The reasoning is that life appeared very early in Earth's history, basically as soon as life could fossilize, we see fossils. Whether it cames from beyond or was created de novo doesn't matter for this discussion. What does matter is that subsequent meteor impacts on Earth would have thrown up plenty of material into space over a very long period of time.

Some bacteria are very resilient and especially in spore form can easily handle being frozen for long periods of time. There are even bacteria that live inside rock, using the energy from radioactive decay to power their chemical processes. They divide very slowly, like once in a century. These could handle space travel without any problem. Given bacterial life has existed for billions of years on Earth, the chances that any solid body in our solar system has not been contaminated from Earth ejecta are very slim.

So any potential environment: salty slurries on Mars, some of the Jovian satellites, maybe the upper atmospheres of Venus and Titan, etc., could harbor life originating from Earth. And it goes even beyond the solar sytem. I've read that the meteor impact that killed the dinosaurs is estimated to have deposited in the order of a tonne of material on the Gliese 5 planets, so if there wasn't life there before, there is now.

What I'm really interested in is whether life orginated on Earth de novo. I think Titan might be key here to discover this, but that's another discussion.

[BDanielMayfield]

I've read that the meteor impact that killed the dinosaurs is estimated to have deposited in the order of a tonne of material on the Gliese 5 planets, so if there wasn't life there before, there is now.

But as you know, or at least should know, you shouldn't believe everything you read Buddy. Panspermia, the idea that life can be naturally spread across space by impacts is very speculative to say the least. Is the assertion that any earth rocks could have been launched clear out of our solar system 65 million years ago even plausible? I doubt it.

Bruce

[Chris Peterson]

I've read that the meteor impact that killed the dinosaurs is estimated to have deposited in the order of a tonne of material on the Gliese 5 planets, so if there wasn't life there before, there is now.

However, some simple analysis reveals that this is complete nonsense. You could vaporize the entire Earth and send the debris spherically outwards, and at 20 light years (the distance to Gliese 581) the mass density would be 10^-5 kg/km². An Earth-sized planet at that distance would collect 360 kg of material. Of course, the Earth wasn't destroyed 65 million years ago. And even if the entire contents of the Chicxulub crater were ejected spherically from the Solar System, the mass density at 20 ly would be just 4 x 10^-5 kg/km². An Earth-sized planet would capture a few hundred milligrams of material.

In reality, however, almost none of the material from that impact would have even escaped Earth's gravitational pull, and less yet the Sun's.

[Buddy]

I've read that the meteor impact that killed the dinosaurs is estimated to have deposited in the order of a tonne of material on the Gliese 5 planets, so if there wasn't life there before, there is now.

However, some simple analysis reveals that this is complete nonsense. You could vaporize the entire Earth and send the debris spherically outwards, and at 20 light years (the distance to Gliese 581) the mass density would be 10^-5 kg/km². An Earth-sized planet at that distance would collect 360 kg of material. Of course, the Earth wasn't destroyed 65 million years ago. And even if the entire contents of the Chicxulub crater were ejected spherically from the Solar System, the mass density at 20 ly would be just 4 x 10^-5 kg/km². An Earth-sized planet would capture a few hundred milligrams of material.

In reality, however, almost none of the material from that impact would have even escaped Earth's gravitational pull, and less yet the Sun's.

It was probably a popular article like this that quoted "1000 pieces" http://www.technologyreview.com/view/42 ... h/?ref=rss. I guess someone equated each piece as a kilogram each, then came up with a tonne, which I remembered seeing somewhere. The original journaled article is here http://arxiv.org/abs/1204.1719.

[moonshiner]

I was considering the apparent angular size of moons in the Solar System from each of the parent planets; the case of the Pluto-Charon system is most intriguing. According to calculations for angular diameter the apparent size of Charon from the surface of Pluto would be approximately 7 times the apparent size of the Moon as viewed from the surface of Earth.
Charon must appear as a faintly lit sphere looming above the Plutonian sky. The Pluto-Charon system presents an opportunity to study the planetary mechanics of gravitationally locked bodies particularly as it serves as a model for terrestrial exoplanets similar to the Earth. I can imagine a terrestrial planet of 11000 km diameter, fourth distant from a G type parent star, accompanied by a gravitationally locked moon of 6000 km diameter at a distance of 80000 km; the period of mutual revolution would probably be about 20 days which would also equal one day and one month on such a system.

[geckzilla]

I've read that the meteor impact that killed the dinosaurs is estimated to have deposited in the order of a tonne of material on the Gliese 5 planets, so if there wasn't life there before, there is now.

However, some simple analysis reveals that this is complete nonsense. You could vaporize the entire Earth and send the debris spherically outwards, and at 20 light years (the distance to Gliese 581) the mass density would be 10^-5 kg/km². An Earth-sized planet at that distance would collect 360 kg of material. Of course, the Earth wasn't destroyed 65 million years ago. And even if the entire contents of the Chicxulub crater were ejected spherically from the Solar System, the mass density at 20 ly would be just 4 x 10^-5 kg/km². An Earth-sized planet would capture a few hundred milligrams of material.

In reality, however, almost none of the material from that impact would have even escaped Earth's gravitational pull, and less yet the Sun's.

It was probably a popular article like this that quoted "1000 pieces" http://www.technologyreview.com/view/42 ... h/?ref=rss. I guess someone equated each piece as a kilogram each, then came up with a tonne, which I remembered seeing somewhere. The original journaled article is here http://arxiv.org/abs/1204.1719.

Never underestimate the willingness of some writers to contrive a story just to get clicks...

[Ann]

I've read that the meteor impact that killed the dinosaurs is estimated to have deposited in the order of a tonne of material on the Gliese 5 planets, so if there wasn't life there before, there is now.

However, some simple analysis reveals that this is complete nonsense. You could vaporize the entire Earth and send the debris spherically outwards, and at 20 light years (the distance to Gliese 581) the mass density would be 10^-5 kg/km². An Earth-sized planet at that distance would collect 360 kg of material. Of course, the Earth wasn't destroyed 65 million years ago. And even if the entire contents of the Chicxulub crater were ejected spherically from the Solar System, the mass density at 20 ly would be just 4 x 10^-5 kg/km². An Earth-sized planet would capture a few hundred milligrams of material.

In reality, however, almost none of the material from that impact would have even escaped Earth's gravitational pull, and less yet the Sun's.

Remember, too, that if some of that life-bearing debris was indeed capable of travelling all the way to the Gliese 5 planets, much more of it would have been able to travel to Mars, which is many orders of magnitude closer to us than Gliese 5.

Also bear in mind that the very much shorter journey to Mars would mean that the bacteria in the Earth fragments had a reasonable, perhaps even good, chance of surviving. What would be the chances of Earth life forms surviving for, we must assume, millions of years travelling slowly through the dry ice cold and cosmic ray-ridden wastes of interstellar space?

If any debris from the Chicxulub crater has made it to the Gliese 5 planets, if its load of life form has survived, and if that life has managed to establish itself and grow a colony on that planet, then surely many more life-bearing "spaceships" should have made it to Mars and delivered Earthly life forms to Mars. There should be many thriving and extended colonies of Earth bacteria on Mars by now. That bacteria should make their presence known to our instruments, both to those that monitor Mars from Mars orbit and to those that have reached the surface of Mars. We should probably even detect clear signals from the Earth that the Martian atmosphere had been modified by all the planet's bacteria.

Where is that very clear evidence of present life on Mars?

Ann

[rstevenson]

Where is that very clear evidence of present life on Mars?

They're hiding. All sensible alien life forms hide from humans. I am not sensible.

Rob

[Nitpicker]

Ann, you're right to state that no life travelled to Gliese 581 (or any other star system beyond ours) from the Chicxulub impact, but not because there isn't any evidence of (current or extinct) life on Mars.

Though your argument is perhaps not quite as convoluted (nor beautiful) as David Bowie's, in his Life on Mars:

It's a god-awful small affair
To the girl with the mousy hair
But her mummy is yelling "No"
And her daddy has told her to go

But her friend is nowhere to be seen
Now she walks through her sunken dream
To the seat with the clearest view
And she's hooked to the silver screen

But the film is a saddening bore
'Cause she's lived it ten times or more
She could spit in the eyes of fools
As they ask her to focus on

Sailors fighting in the dance hall
Oh man! look at those cavemen go
It's the freakiest show

Take a look at the lawman
Beating up the wrong guy
Oh man! Wonder if he'll ever know
He's in the best selling show
Is there life on Mars?

It's on America's tortured brow
That Mickey Mouse has grown up a cow
Now the workers have struck for fame
'Cause Lennon's on sale again

See the mice in their million hordes
From Ibiza to the Norfolk Broads
Rule Britannia is out of bounds
To my mother, my dog, and clowns

But the film is a saddening bore
'Cause I wrote it ten times or more
It's about to be writ again
As I ask you to focus on

Sailors fighting in the dance hall
Oh man! Look at those cavemen go
It's the freakiest show

Take a look at the Lawman
Beating up the wrong guy
Oh man! Wonder if he'll ever know
He's in the best selling show
Is there life on Mars?

Source: http://www.metrolyrics.com/life-on-mars ... bowie.html

[Buddy]

Where is that very clear evidence of present life on Mars?

Ann

It would be erroneous to expect a teeming biosphere on Mars. If the deserts of Antarctica by comparison are a tropical paradise, and life is just barely surviving in that environment with billions of years of evolution behind it, then we shouldn't expect any more than that on Mars.

As far as clear current evidence, the trace amounts of methane are a good one. ExoMars and other future missions should provide more definitive results. Apparently a reanalysis of the Viking results in light of current knowledge is pointing more towards the direction of biological origins as opposed to entirely inorganic origins. If the lifeforms are mostly endolithic, with very low metabolisms, as they are on Earth, it would be difficult to find them, as is the case on Earth.

Just a note, until Earth's bacteria started producing an abundance of oxygen about 2 billion years ago, it would have been difficult to determine without detailed chemical analyses of the soil that there was life on the planet, even though it had already existed for more than a billion years. If one knew what to look for one might recognize stromatolites in tidal zones as something other than strange rocks, but that's about it. The surface would have looked barren, like the deserts of Antarctica.

Interesting and related article http://discovermagazine.com/1997/may/lo ... lifein1124.

[geckzilla]

The trace amounts of methane are a good one.

The evidence for which is currently in doubt. Curiosity has yet to find any. Of course, we need to keep looking.

[Ann]

Ann, you're right to state that no life travelled to Gliese 581 (or any other star system beyond ours) from the Chicxulub impact, but not because there isn't any evidence of (current or extinct) life on Mars.

Though your argument is perhaps not quite as convoluted (nor beautiful) as David Bowie's, in his Life on Mars:

It's a god-awful small affair
To the girl with the mousy hair
But her mummy is yelling "No"
And her daddy has told her to go
...

Take a look at the lawman
Beating up the wrong guy
Oh man! Wonder if he'll ever know
He's in the best selling show
Is there life on Mars?
...

Sailors fighting in the dance hall
Oh man! Look at those cavemen go
It's the freakiest show
...
Is there life on Mars?

Source: http://www.metrolyrics.com/life-on-mars ... bowie.html

Yes, that's a good one. But I prefer Chris Hadley singing the Space Oddity.

Click to play embedded YouTube video.

Ann

[Ron-Astro Pharmacist]

Very retinal..

Retina.jpg (2.58 KiB) Viewed 159114 times

but frozen. I'm sure we'll keep an eye on Europa for further exploration.