Dynamics of escaping Earth ejecta ...

[A.DIM]

I don't see where they've made theoretical breakthroughs. They might have run longer simulations, which is a different thing.

Yes, they do say they've done more extensive simulations, and yet, the numbers are quite small. That's why I'm concerned about the statement I quoted, that "However, as also noted in their paper, our results for Mars are within the known typical errors of such probability estimations."

Think of it this way: If your study shows two impacts out of 10,000, and an older study shows one impact out of 10,000, you can say your study shows twice as many impacts. And yet, it's still a small number, so it could just be within the error boundaries and be entirely meaningless. They're probably going to need to do longer simulations to show that their increase isn't just noise, and, of course, they will need to show they haven't introduced errors into the process.

I understand and don't disagree, but I think their intent was more to verify Gladman's results rather than break through theory; peer review if you will. Certainly I'm interested to see how their future work "to determine the statistical significance of these results" - particles reaching Mars and Jupiter - shakes out but personally, I don't doubt material from Earth reaches multiple bodies in our system, even while the number may be small. The question in my mind is whether what gets there is dead or alive.
Do you not think Earth ejecta can reach Mars, or perhaps moons of Jupiter?

[R.A.F.]

....personally, I don't doubt material from Earth reaches multiple bodies in our system, even while the number may be small.

I don't doubt that, either.

The question in my mind is whether what gets there is dead or alive.

Good question.

Do you not think Earth ejecta can reach Mars, or perhaps moons of Jupiter?

Well, if we're going to "play" statistics/odds...taking into account the massive gravity well that is the Sun, wouldn't it be more "likely" that of any material, ejected, the majority of that material would fall further into the Solar System?...to perhaps Venus and Mercury??

So why single out Mars and the satellites of Jupiter?

[PaulLogan]

So why single out Mars and the satellites of Jupiter?

from the bbc article:

The real question is whether any ejecta will carry living cargo that can fulfil the "panspermia" hypothesis, but Dr Sigurdsson says that evidence of the hardiness of life has already been found closer to home.

it seems to me they focused on mars and the jupiter satellites because they are considered the most likely candidates for having (or having had) conditions that may support life.
the article does not mention they focused exclusively on those objects.

[A.DIM]

I don't doubt that, either.

Then why all the squawking at the outset?

Good question.

It most certainly is, and deserves serious scientific consideration.

Well, if we're going to "play" statistics/odds...taking into account the massive gravity well that is the Sun, wouldn't it be more "likely" that of any material, ejected, the majority of that material would fall further into the Solar System?...to perhaps Venus and Mercury??

What does "play" statistics / odds mean? Is that what you consider N-body simulations to be? Did you not read the paper, or even the abstract?

From the abstract:
The Mercury 6 code is used to compute the dynamics of test particles under the gravitational effect of the inner
planets in the Solar System and Jupiter. A series of simulations are conducted with different ejection velocity, considering
more than 10^4 particles in each case. We find that in general, the collision rates of Earth ejecta with Venus and
the Moon, as well as the fall-back rates, are consistent with results reported in the literature. By considering a larger
number of particles than in all previous calculations we have also determined directly the collision probability with
Mars and, for the first time, computed collision probabilities with Jupiter. We find that the collision probability with
Mars is greater than values determined from collision cross section estimations previously reported.

and from Part 2. Model description:

We consider ejecta as test particles moving under the action of the gravitational field of the Sun, the Moon, and all planets of the Solar System. No other forces are considered in the present study. Particles are assumed not to collide with each other, but may impact any of
the massive bodies. The dynamics of the planets and test particles system is calculated using the Mercury 6.2 code developed by Chambers (1999).

Do you have a reason to suspect their calculations, or the code they used, is in err?

So why single out Mars and the satellites of Jupiter?

Uh, because they're the most likely candidates for habitable environments ...
was that a serious question?

Here's why.

[Van Rijn]

I believe the article looks at impact probabilities for Venus, Earth, the Moon, Mars, and Jupiter. There is not, as far as I'm aware, anything in the article about Jupiter's moons (which are, of course, far smaller targets than Jupiter). The article does mention the far higher impact velocities you'd have for Jupiter versus Mars, which (even if the planet Jupiter were potentially habitable) would be a serious problem for transferring living material.

[A.DIM]

I believe the article looks at impact probabilities for Venus, Earth, the Moon, Mars, and Jupiter. There is not, as far as I'm aware, anything in the article about Jupiter's moons (which are, of course, far smaller targets than Jupiter). The article does mention the far higher impact velocities you'd have for Jupiter versus Mars, which (even if the planet Jupiter were potentially habitable) would be a serious problem for transferring living material.

In the Discussion the authors do mention Europa and Ganymedes (sic) when pointing out the astrobiological significance of their results, but say nothing else. No doubt they will be considered in future modeling.
I need to reread Survivability of Bacteria in Hypervelocity Impact to be sure, but I'd guess the speeds we're talking won't necessarily be lethal.

[R.A.F.]

Then why all the squawking at the outset?

Can't really answer that question, and it's not because I don't have an answer.

It most certainly is, and deserves serious scientific consideration.

That's debatable...

What does "play" statistics / odds mean?

It means...if I were to speculate, then I would have to say there is more of a likelyhood of material moving toward the Sun rather than away from it based on gravity. That and because Jupiter and it's satellites are really far away.

Is that what you consider N-body simulations to be? Did you not read the paper, or even the abstract?

So you expect me to "just accept it" even though it is counter-intuitive?

Sorry...not wired that way...

[PaulLogan]

It most certainly is, and deserves serious scientific consideration.

That's debatable...

no, it isn't. not for a scientist anyways. the possibility of extraterrestrial life is one of the most fundamental and fascinating questions.

It means...if I were to speculate, then I would have to say there is more of a likelyhood of material moving toward the Sun rather than away from it based on gravity. That and because Jupiter and it's satellites are really far away.

clearly, that is not what they found in the simulations. whether you find them counter-intuitive or not, the numbers don't lie.

So you expect me to "just accept it" even though it is counter-intuitive?

Sorry...not wired that way...

guess what? nature doesn't care if you or anybody else finds it counter-intuitive. check out quantum physics.
i guess you are not "wired" for science then...

[A.DIM]

Can't really answer that question, and it's not because I don't have an answer.

Forget I asked; I'm not really interested.

That's debatable...

Eh? You say it is a good question and then follow with "that's debatable" as to whether or not it deserves serious scientific consideration?

It means...if I were to speculate, then I would have to say there is more of a likelyhood of material moving toward the Sun rather than away from it based on gravity. That and because Jupiter and it's satellites are really far away.

Well, according to their models, of the 5 scenarios, 0% ejecta fall into the sun in four of them. Only the high velocity event which sends material to Jupiter also results in material falling into the sun.
You didn't even look at the chart they provide, did you?

So you expect me to "just accept it" even though it is counter-intuitive?

No. I expect you to read the paper and have a little more insight into the material you argue against, or for, whichever .... if it's a "good question."

Sorry...not wired that way...

I can only imagine the schematic ...

[R.A.F.]

no, it isn't. not for a scientist anyways. the possibility of extraterrestrial life is one of the most fundamental and fascinating questions.

...with no supportive evidence....fascinating...

whether you find them counter-intuitive or not, the numbers don't lie.

Oh really??


Let's look at the "if's"...

"If" the Earth was impacted in just the right place...and

"If" that ejected material contained life...and

"If" that ejected material moved against gravity toward the outer system...and

"If" it came anywhere near Mars, or Jupiter...and

"If" that life could survive the travel time...


With all these unproven "If's", and you can't understand my skepticism?

i guess you are not "wired" for science then...

I'll let the mods handle this...

[R.A.F.]

Forget I asked; I'm not really interested.

Hey..I knew that.

Eh? You say it is a good question and then follow with "that's debatable" as to whether or not it deserves serious scientific consideration?

Paradoxically, the older I get, the more irrelevant "the ET life question" is to me. I figure I have maybe 30 years left here, and I just don't think the "question" will be answered in that time.

So...to me...not that interesting...

...according to their models...

So these models have been real world proven beyond ANY doubt?

Seriously doubt that...

...of the 5 scenarios, 0% ejecta fall into the sun in four of them...

,,,and that seems rational to you?

[PaulLogan]

...with no supportive evidence....fascinating...

wow! so, according to you, without supportive evidence science is not supposed to ask questions?

Oh really??


Let's look at the "if's"...

"If" the Earth was impacted in just the right place...and

"If" that ejected material contained life...and

"If" that ejected material moved against gravity toward the outer system...and

"If" it came anywhere near Mars, or Jupiter...and

"If" that life could survive the travel time...


With all these unproven "If's", and you can't understand my skepticism?

don't change subject. you were questioning their results because you found them counter-intuitive.
you were not questioning their methodology.
n-body simulation is a tried and tested method applied in many areas of physics and especially in astrophysics.
there are always ifs in simulations; it's inherent and unavoidable.
and some of your ifs simply show that you do not understand the method the used.
e.g.

"If" the Earth was impacted in just the right place...

not an assumption. that's part of the simulation. they simulated projectiles coming from different (random) angles and with different (random) velocities.

"If" that ejected material moved against gravity toward the outer system...
"If" it came anywhere near Mars, or Jupiter...

again: no assumption, those are results of the simulation.

Guess you're not wired to argue a "point" without being insulting...

yeah, sorry about that. couldn't resist dishing you some of the insults you so freely dish out on this forum but i shouldn't have.

[R.A.F.]

don't change subject. you were questioning their results because you found them counter-intuitive.

Yes...as anyone without bias would.

you were not questioning their methodology.

So you get to decide what I can, and what I can't post? Careful Icarus.

...there are always ifs in simulations; it's inherent and unavoidable.

Then why the conscious choice to ignore those "if's"?

...and some of your ifs simply show that you do not understand the method the used.

Method?? So my questions are ignorant? I think you were better off with sticking with your previous insult.

...they simulated projectiles coming from different (random) angles and with different (random) velocities.

With non-random results?? Does this really make sense to anyone other than the current participants in this thread??

yeah, sorry about that. couldn't resist dishing you some of the insults you so freely dish out on this forum but i shouldn't have.

Accepted....I think..

[Van Rijn]

"If" that ejected material contained life...and

I'm afraid this "if" is outside the scope of the paper's argument. It's specifically modeling material transfer and impact probabilities. If they get something wrong, it would be because they made an error in calculation, didn't have enough precision, or something of that nature.

"If" that ejected material moved against gravity toward the outer system...and

"If" it came anywhere near Mars, or Jupiter...and

RAF, this is what the paper is modeling. It starts with groups of particles near Earth with substantial starting velocities (the simulated effect of a large impact on Earth - see the paper for the justification of the starting conditions). The velocities are such that much of the material can escape Earth and move in as well as out-system. They follow the particles and see where they end up over time.

[korjik]

no, it isn't. not for a scientist anyways. the possibility of extraterrestrial life is one of the most fundamental and fascinating questions.



clearly, that is not what they found in the simulations. whether you find them counter-intuitive or not, the numbers don't lie.



guess what? nature doesn't care if you or anybody else finds it counter-intuitive. check out quantum physics.
i guess you are not "wired" for science then...

If numbers didnt lie, I would have proved the universe dosent exist three or for times now. Numbers will lie all over the place if they arent treated right.

Also, counterintuitive means different things to different people. What a scientist thinks is counterintuitive isnt what you will think is counterintuitive.

[Van Rijn]

With non-random results?? Does this really make sense to anyone other than the current participants in this thread??

Non-random? I'd call them probabilistic results.

[Van Rijn]

In the Discussion the authors do mention Europa and Ganymedes (sic) when pointing out the astrobiological significance of their results, but say nothing else.

They really shouldn't have mentioned them at all, given the scope of the model.

I need to reread Survivability of Bacteria in Hypervelocity Impact to be sure, but I'd guess the speeds we're talking won't necessarily be lethal.

That appears to be looking at the effect of velocity [edit: that should be "extreme acceleration"] on the function of bacteria, and the velocities seem to be more in the range of what you'd get with Earth or Mars. I was thinking of the problem of atmospheric entry heating - a big issue with Jupiter.

[Jim]

yeah, sorry about that. couldn't resist dishing ... but i shouldn't have.

Accepted...

I'm glad you two worked this out before someone(s) got in trouble.

[A.DIM]

...with no supportive evidence....fascinating...

Science is the method we use to understand and describe ourselves, the world we live in, the cosmos. I find it fascinating, from a social science perspective, that one could suggest the search for life elsewhere is not a worthy
scientific pursuit.
And of course you understand our single example of life in the universe tells us exactly nothing about its prevalence?

Oh really??

Let's look at the "if's"...

"If" the Earth was impacted in just the right place...and

What do you mean by "just the right place?"

It is thought Impact Event, a large one, occurs every 10 million years. So, of those that we know of, which do you think were not in "just the right place?"

"If" that ejected material contained life...and

What?!
Life is in every nook and cranny of the Earth's crust. Where do you think no life persists?
Read up on Tardigrades and B Subtillis.

"If" that ejected material moved against gravity toward the outer system...and

"If" it came anywhere near Mars, or Jupiter...and

Well, there is this new study, which builds on others, and shows more material and a higher probability than previously thought ...

"If" that life could survive the travel time...

Yes! A good question.

With all these unproven "If's", and you can't understand my skepticism?

I think understand it, RAF, all too well.
I just don't think it's based on much, let alone "all these unproven "Ifs"

[A.DIM]

They really shouldn't have mentioned them at all, given the scope of the model.

Indeed I found it curious, perhaps foreshadowing future studies.

That appears to be looking at the effect of velocity on the function of bacteria, and the velocities seem to be more in the range of what you'd get with Earth or Mars. I was thinking of the problem of atmospheric entry heating - a big issue with Jupiter.

Yes you're right, the velocities appear lower in that study. And I wonder what kind of temperatures could be reached in entering Jupiter's atmosphere. Of course, that depends on velocity and impact speeds, angle, leading or trailing face ...
yeah, at this time, it appears only detritus would reach Jupiter.

[Luckmeister]

Paradoxically, the older I get, the more irrelevant "the ET life question" is to me. I figure I have maybe 30 years left here, and I just don't think the "question" will be answered in that time.

So...to me...not that interesting...

Then why do you bother to take part in this discussion? Actuaries predict that I have maybe 5 to 10 years left, so should I argue against any project or study that will take longer on that basis? Of course not.

[R.A.F.]

Then why do you bother to take part in this discussion? Actuaries predict that I have maybe 5 to 10 years left, so should I argue against any project or study that will take longer on that basis? Of course not.

I'm not arguing against any...oh never mind...


I'll be back (to this thread) in time for Rosh Hashanah

[A.DIM]

Really, you came back half an hour later to add "(to this thread)" ??

What's the point in that post to begin with?
I don't give two sheets about Rosh Hashanah or the Judeo Christian mythos.
Keep that tripe out of my thread please.
Thanks.

[R.A.F.]

I don't give two sheets about Rosh Hashanah...

We will see...

[Swift]

I'll be back (to this thread) in time for Rosh Hashanah

I don't give two sheets about Rosh Hashanah or the Judeo Christian mythos.

Is it possible for you two to behave? Both of you keep this stuff out of the thread and stick with the topic. And I know both of you know how to report posts if you have problems with the others' posts. You both get zero point infractions for this.

[R.A.F.]

Is it possible for you two to behave? Both of you keep this stuff out of the thread and stick with the topic. And I know both of you know how to report posts if you have problems with the others' posts. You both get zero point infractions for this.

Sorry, Swift...I had hoped that A.DIM would note the "significance" of the date Rosh Hashanah falls on, but i guess not....

[A.DIM]

Yeah, sorry Swift (for responding in-kind).
RAF intended no religious context in posting that.
He's simply looking forward to the day that my thread gets locked.

[John Mendenhall]

Gentle folk, it's a delightful idea, but until we get to Mars, and pick up a meteorite from Earth, and find viable spores inside, it's speculation. But oh my, I do hope it turns out to be true!

[grapes]

I'm here to loc... OK, we'll try one more time.

[R.A.F.]

You'll regret it...

A.DIM...if you have something you want to discuss, do so on the open board.

In other words, I have nothing to discuss with you via PM, so you might as well stop sending them.