Rosetta, Philae and Comet 67P/Churyumov-Gerasimenko.

[Kryten]

It was given as a talk at an astronomy conference, which I haven't been able to directly find online, but almost all the buzz has been from this Guardian article, which a bunch of other newspapers shamelessly copied.

[lajoswinkler]

You might want to read up on panspermia, since you seem to be misjudging some probabilties and possibilities. People much more adept than you and I have looked into this and, until now, have found no reason to believe it is not reasonably possible (though different experts will of course have different opinions). That does not mean it has happened, it simply means it still on the table.

The numbers involved are quite mind-boggling indeed, I can imagine you have trouble wrapping your head around those.

You might want to read up on biology and microbiology. Panspermia is about stuff trapped in planetary debris, not naked spores behaving like Superman.

I repeat, zero chance for a naked spore to survive that and I stand behind that. If you can prove I'm wrong, you're free to do it.

[peadar1987]

Basically, a "scientist" with a long track record for crackpottery said he had "unequivocal evidence" that carbon deposits on the comet meant the presence of life, without going any further into what that evidence may have been.

[Kryten]

The evidence is the organic deposits. This is the same guy that thought microbes being found at 40km altitude means those microbes must be extraterrestrial, leaps of logic are his MO.

[Aethon]

I don't opine much here lately because of the usual violent negative responses, but I have read quite a lot about panspermia so here goes...

IMO, no known life form would survive naked in space, primarily due to radiation and it's effect on DNA. That's not to say that certain life forms, safely encased in a large rock couldn't survive ejection as a meteorite, and long enough to encounter another suitable planet. This is highly unlikely, due to encounter times and interplanetary reentry speeds, but by no means impossible. I do however believe panspermia can and does happen, in certain situations, over vast time spans.

In the list of things man left on the moon you'll find -96 bags of feces, urine and vomit. Now I'm not saying than anything in those bags lived very long, (The Poop Monsters of Apollo 11), or that this mechanism is likely to be repeated in other solar systems, but it's a concrete example of the mechanism at work.

If we examine the speed at which we currently encounter interstellar debris, it is highly unlikely any life bearing rock could survive a collision with a planet intact, let alone geologic periods of time in space.

However there was a time many billions of years ago, (perhaps around the time life took hold on Earth) when our sun and proto planets were nestled in a cloud of stars that would boggle the mind. The skies were ablaze with a thousand suns, much closer than the stars we see now. Interstellar sharing of material was much more common and encounter speeds were much lower than today. I like to speculate that one of our older sister clustermates could have been 'infected' with life, which spread throughout our cluster, which then smeared life throughout the galaxy during cluster dispersal.

Edited July 9, 2015 by Aethon

[YNM]

You mean hypotheses. These are not theories. Theories have evidence.

Thanks for the correction !

Anyway, can we get out of this discussion ? Rosetta's mission isn't for biological activities, it's for physical activities (ie. venting, sublimating, composistion etc). If you want to tell whether life can survive on a comet, send some suggestion to space agencies for follow up cometary mission maybe, specifically for the subject ?

EDIT: wrt panspermia, I don't want to say anything about organism, I only point that you can exchange (complex) molecules via debris. Not necessarily important to life, but molecules are possible - ends up as minerals or sediments. Doesn't mean life can form equally on the other side though.

Edited July 9, 2015 by YNM

[Camacha]

You might want to read up on biology and microbiology. Panspermia is about stuff trapped in planetary debris, not naked spores behaving like Superman.

Ah, you are making up conditions that suit your story. Yeah, sure, in that case you can generally come up with something that fits your needs

I repeat, zero chance for a naked spore to survive that and I stand behind that. If you can prove I'm wrong, you're free to do it.

Absolute statements require absolute evidence. You make the claim, you substantiate it. Those are the simple basics of science.

[PB666]

In space a spore would undergo dehydration, and dehydration would preserve its activity. It prolly would not survive re-entry into a world outside of being a deposit in the core of some asteroid. Cometary fragments blow up on reentry, the temperature would be to high for DNA or protein to survive. Ionizing radiation from cosmic rays are problematic but survivable for crude life forms, its the stuff of evolution anyway. It is certainly in the realm of plausibility, but given the conditions required to get something into a transplanetary orbit.

One thing about re-entry a particle of a small size, that has been dessicated to the max, relatively fluffy could enter earths upper atmosphere at an oblique angle as long as it had a surface capsule protecting it from ablation could slow down sufficiently not to burn up on re-entry. Its surface area to mass it quite large, and thus it would decelerate quite rapidly, it would need to withstand the onslaught of 8000 m/s particles for a short period but once it slowed down below 1000 m/s it could survive reentry into the troposphere boundary. Even if the life did not survive its DNA could be picked up by bacteria and incorporated into bacterial genomes.

THis is what is an if and if and if and if argument. If a life form was dislodged from a habitable planet, and if it that said life-form had a dessicated spore state, and if the life form happened to be on an interplanetary trajectory and if it transected earths upper atmosphere at the right angle, and if it was strenuous enough to survive reentry then ... . . . . ..

Not likely.

[Camacha]

Cometary fragments blow up on reentry, the temperature would be to high for DNA or protein to survive.

People have said this before, but it has been empirically proven that all elements of lithospermia are, at least when conditions are right, possible. Wikipedia tells us what we need to know for now:

Lithopanspermia

Lithopanspermia, the transfer of organisms in rocks from one planet to another either through interplanetary or interstellar space, remains speculative. Although there is no evidence that lithopanspermia has occurred in our own Solar System, the various stages have become amenable to experimental testing.[56]

Planetary ejection  For lithopanspermia to occur, microorganisms must survive ejection from a planetary surface which involves extreme forces of acceleration and shock with associated temperature excursions. Hypothetical values of shock pressures experienced by ejected rocks are obtained with Martian meteorites, which suggest the shock pressures of approximately 5 to 55 GPa, acceleration of 3×106 m/s2 and jerk of 6×109 m/s3 and post-shock temperature increases of about 1 K to 1000 K. To determine the effect of acceleration during ejection on microorganisms, rifle and ultracentrifuge methods were successfully used under simulated outer space conditions.

Survival in transit  The survival of microorganisms has been studied extensively using both simulated facilities and in low Earth orbit. A large number of microorganisms have been selected for exposure experiments. It is possible to separate these microorganisms into two groups, the human-borne, and the extremophiles. Studying the human-borne microorganisms is significant for human welfare and future manned missions; whilst the extremophiles are vital for studying the physiological requirements of survival in space.

Atmospheric entry  An important aspect of the lithopanspermia hypothesis to test is that microbes situated on or within rocks could survive hypervelocity entry from space through Earth's atmosphere (Cockell, 2008). As with planetary ejection, this is experimentally tractable, with sounding rockets and orbital vehicles being used for microbiological experiments. B. subtilis spores inoculated onto granite domes were subjected to hypervelocity atmospheric transit (twice) by launch to a ∼120 km altitude on an Orion two-stage rocket. The spores were shown to have survived on the sides of the rock, but they did not survive on the forward-facing surface that was subjected to a maximum temperature of 145 °C. In separate experiments, as part of the ESA STONE experiment, numerous organisms were embedded in different types or rocks and were mounted in the heat shield of six Foton re-entry capsules. During reentry, the rock samples were subjected to temperatures and pressure loads comparable to those experienced in meteorites. The exogenous arrival of photosynthetic microorganisms could have quite profound consequences for the course of biological evolution on the inoculated planet. As photosynthetic organisms must be close to the surface of a rock to obtain sufficient light energy, atmospheric transit might act as a filter against them by ablating the surface layers of the rock. Although cyanobacteria have been shown to survive the desiccating, freezing conditions of space in orbital experiments, this would be of no benefit as the STONE experiment showed that they cannot survive atmospheric entry. Thus, non-photosynthetic organisms deep within rocks have a chance to survive the exit and entry process. (See also: Impact survival.) Research presented at the European Planetary Science Congress in 2015 suggests that ejection, entry and impact is survivable for some simple organisms.

THis is what is an if and if and if and if argument. If a life form was dislodged from a habitable planet, and if it that said life-form had a dessicated spore state, and if the life form happened to be on an interplanetary trajectory and if it transected earths upper atmosphere at the right angle, and if it was strenuous enough to survive reentry then

You forget the time scale. Bodies will get hit by large rocks, ejecta will spread throughout a system and beyond over enough time and some of it will hit other bodies. Those are a given. The wild cards are whether life has formed somewhere and how likely it is to survive these conditions. Unfortunately, the former is nearly impossible to answer without us finding other life, and the latter is a bit of a guessing game with just one life 'family' available for testing.

If there is one thing nature and the universe has plenty of, it is time.

[Kryten]

There's no plausible way for a microorganism to survive the radiation exposure over very long periods of time involved with interplanetary transit. Highly radiation-tolerant organisms like the much-vaunted Deinococcus radiodurans all have active DNA repair mechanisms-they wouldn't help in a dormant state.

[Camacha]

There's no plausible way for a microorganism to survive the radiation exposure over very long periods of time involved with interplanetary transit. Highly radiation-tolerant organisms like the much-vaunted Deinococcus radiodurans all have active DNA repair mechanisms-they wouldn't help in a dormant state.

What is the source of the information you base your statements on? I will point to the same page again, which seems to tell us something different:

Then, data gathered by the orbital experiments ERA, BIOPAN, EXOSTACK and EXPOSE, determined that isolated spores, including those of B. subtilis, were killed by several orders of magnitude if exposed to the full space environment for a mere few seconds, but if shielded against solar UV, the spores were capable of surviving in space for up to 6 years while embedded in clay or meteorite powder (artificial meteorites).] Though minimal protection is required to shelter a spore against UV radiation, exposure to solar UV and cosmic ionizing radiation of unprotected DNA, break it up into its bases. Also, exposing DNA to the ultrahigh vacuum of space alone is sufficient to cause DNA damage, so the transport of unprotected DNA or RNA during interplanetary flights is extremely unlikely.

Based on experimental data on radiation effects and DNA stability, it has been concluded that for such long travel times, boulder sized rocks which are greater than or equal to 1 meter in diameter are required to effectively shield resistant microorganisms, such as bacterial spores against galactic cosmic radiation. These results clearly negate the radiopanspermia hypothesis, which requires single spores accelerated by the radiation pressure of the Sun, requiring many years to travel between the planets, and support the likelihood of interplanetary transfer of microorganisms within asteroids or comets, the so-called lithopanspermia hypothesis.

Radiopanspermia seems less likely, at least for the type of RNA/DNA that is found on our planet. Maybe that other types of genetic structure will fare better, but those will unlikely have seeded Earth to start life here, since that should be the type of genetic material found.

Edited July 9, 2015 by Camacha

[Master Tao]

Folks,

Even though there hasn't been much official news in the past week, let's keep to the topic of the Rosetta mission. You can subscribe to the thread so you'll see when it's updated.

[Camacha]

Folks,

Even though there hasn't been much official news in the past week, let's keep to the topic of the Rosetta mission. You can subscribe to the thread so you'll see when it's updated.

Is this an official moderator statement, or are you posting this as a user?

[Frida Space]

Rosetta was scheduled to attempt a CONSERT radio contact with Philae yesterday (Wednesday 7th). Waiting for a statement now. If the attempt failed, it would be 16 days since the last contact.

[Vanamonde]

Is this an official moderator statement, or are you posting this as a user?

If we're asking you to stick to the topic or reminding you of forum rules, it's official.

[Camacha]

Rosetta was scheduled to attempt a CONSERT radio contact with Philae yesterday (Wednesday 7th). Waiting for a statement now. If the attempt failed, it would be 16 days since the last contact.

I was glad to see contact reestablished, but it looks like the cheers were somewhat preemptive. It seems to be rather hard to contact Philea again and with any reliability.

If we're asking you to stick to the topic or reminding you of forum rules, it's official.

Since trouble has arisen from different interpretations before, I/forum posters are wise not to leave anything to chance any more.

Edited July 10, 2015 by Camacha

[Frida Space]

I was glad to see contact reestablished, but it looks like the cheers were somewhat preemptive. It seems to be rather hard to contact Philea again and with any reliability.

Was it really reestablished? I missed the news! Great.

[Frida Space]

Rosetta has confirmed via twitter it has re-established a signal with Philae. "Details to follow"

http://twitter.com/DLR_en/status/619483893280940032

http://twitter.com/esaoperations/status/619485131980587008

- - - Updated - - -

Here it is: http://blogs.esa.int/rosetta/2015/07/10/new-communication-with-philae-commands-executed-successfully/

Edited July 10, 2015 by Frida Space

[Camacha]

Was it really reestablished? I missed the news! Great.

I have rarely been cheering a piece of hardware on so vigorously

[Frida Space]

I have rarely been cheering a piece of hardware on so vigorously

hahaha, same here!

[Sharpy]

Oh yessss!

From the very guarded statements they were making when they lost contact I could sense they didn't believe it would wake up. But - yeah!

Post when they get some new photos!

BTW, more than the twitter messages: http://blogs.esa.int/rosetta/2015/07/10/new-communication-with-philae-commands-executed-successfully/

Edited July 10, 2015 by Sharpy

[YNM]

Does cometary dust somehow affected the signal ? Maybe it didn't reach Philae because of reflectance and/or absorption, considering it's water ice?

[Frida Space]

Does cometary dust somehow affected the signal ? Maybe it didn't reach Philae because of reflectance and/or absorption, considering it's water ice?

CONSERT is designed to study the radio link from Rosetta to Philae and back through the comet nucleus, so my guess is that small particles can't affect it.

[Shpaget]

CONSERT is designed to study the radio link from Rosetta to Philae and back through the comet nucleus, so my guess is that small particles can't affect it.

That in itself doesn't tell us much. You can spend a lifetime studying the radio link through the Earth only to discover one after another reason why it doesn't work, or why the link quality doesn't meet your needs.

That being said, CONSERT is up and running.

[Frida Space]

I'm sorry, I had to. 1000 posts!

- - - Updated - - -

That in itself doesn't tell us much. You can spend a lifetime studying the radio link through the Earth only to discover one after another reason why it doesn't work, or why the link quality doesn't meet your needs.

That being said, CONSERT is up and running.

How is that related to what I said? I was stating that, because the CONSERT instrument is designed (and has already proved it works) to pass through the nucleus, I'm assuming it shouldn't have any problems passing through a dust particle. Plus, we already linked that press release twice above your post.