Hacker News Reader

Comment by TrainedMonkey | Hacker News Reader

From the simulation you linked looks like it is passing closeish to the Mars... but I do know that space is big. However, I am curious of what would happen if an object of this magnitude hit mars at 90km/s.

View on HN

Would be wild if a sufficiently large object with a lot of water and organic molecules hit Mars, ejected a lot of material in to Mars’ orbit to then go on to form a sufficiently large moon that tidally massaged Mars’ core to cause a dynamo to generate a sufficiently strong magnetic field to…

Terraform Mars!

You don't need a magnetic field to terraform Mars, it can hold onto an atmosphere without it for 100M years.

Without a magnetic field, isn’t the surface of Mars subject to sterilising radiation from Sol?

Planetary magnetic field only weakly protects against cosmic rays (extra-solar origin).

A thick enough atmosphere will stop pretty much all the charged particles from the normal solar radiation.

If it would be so bad, Earth's polar regions (experiencing aurora borealis) would be inhabitable too. Earth's magnetic field is not magically neutralizing all charged particles from the Sun, just diverts them (some maybe away, but many simply towards poles).

And clearly even our mag field (and Sun's heliosphere) is not enough to shield us from those crazy cosmic rays.

in a somewhat related story, I was on a beach in Costa Rica last week, watching some spider monkeys in a palm tree trying to whack open small nuts. Just then, an American family walked up the beach with two teenage boys. They didn't notice the monkeys I was watching. But one of the boys grabbed a coconut off the sand and became determined to break it open with a rock in front of his parents. So watching the monkeys and the boy simultaneously, I had the distinct feeling of how slowly evolutionary, let alone geological, processes actually move.

Haha, cool, that gave me a chuckle :)

“We'll be saying a big hello to all intelligent lifeforms everywhere and to everyone else out there, the secret is to bang the rocks together, guys.” - The Hitchhikers Guige to the Galaxy, Douglas Adams

Gag Halfront, wasn’t it?

Max Quordlepleen

Nice story.

But are you implying that we are somehow more evolved than the monkeys? Both the human and the monkey in the story have evolved for the same amount of time since our last common ancestor.

That argument always struck me as vacuous. Dump a barrel of ball bearings on the top of a craggy hill. Wait as they all bounce around, some getting stuck in local minima and some bouncing over obstacles and covering large distances.

Would you claim that they all traveled the same distance because they all traveled for the same amount of time?

Evolutionary space is very high dimension, which makes the argument that just projecting onto the (1d) time axis is misleading even stronger.

I'm not sure more/less evolved is a meaningful concept in Darwinian terms. Organisms have a level of fitness for their environment. Perhaps you are talking about cultural evolution?

Do not we humans and those monkeys largely share the same environment?

Which one is more numerous, less prone to natural forcings?

frame of reference matters, from the center of the sun or galactic core they all most certainly moved the same distance in the same amount of time and it was much further than the hill was tall.

Sure? What is the analog to this other frame of reference in the evolution case though? Or are you just stepping out of the analogy's applicability range to show that it can be pushed too far (which is of course true of an analogy)?

A Molecular clock would be gravity in your model, when ever you called stop all your marbles would have experienced the same amount of gravitational force. That is the intent of "experienced the same amount of evolution" and similar.

Where I see the model flounder is; the hill provides the fitness context. You implied distance "means" more evolved, but for life it is all about making it to the next round, in your marble game how many of those furthest marbles will ever be found for the next round?

With life big changes are dangerous, you may find yourself improved out of options.

What is easier? Not mess up this planet, or Terraform Mars?

Username checks out.

I don't know. Have you seen humanity? I think teraforming another planet is probably easier than not fucking up this one

Belter, our future is in orbital habs. Going downwell is for tourism and archaeology.

Can you walk and chew gum?

It’s not worth doing because it is easier, but because all of our eggs are in one basket (planet). We know of disasters that can wipe out almost all life on a single planet. Of course, there are also disasters that can wipe out all life in one star system (and one region of the Galaxy). So, ideally we need to colonize many worlds in many different parts of the Galaxy, but baby steps. Step one is to have a sustainable population on multiple moons/planets/stations of this star system before we jump to other star systems.

Vastly easier to not only stop but also undo all the damage here than to do anything of consequence on Mars.

Would be pretty hard to fuck up Mars’ biosphere.

The best way I heard this put: Before we worry about terraforming Mars, maybe first we should stop Venusforming Terra.

Assuming it’s at the upper range of the size estimate above, and of average rocky density, the kinetic energy of the impact would be something like a 10 billion megaton nuke.

If we could steer it to hit one of Mars’s poles, it might do a bit of terraforming for us!

Where did my math go wrong? I got about 50,000 megatons. Assuming the high-end of 22km and a rocky/metallic density of 5000 kg/cubic meter (and assuming it's a cube):

  kinetic energy = 1/2 m v**2 = 1/2 * size * density * v**2
  = 1/2 *(22000 m)**3 * (5000 kg/m**3) * (90 m/s)**2 / (4.184E15 J/megaton)
  = 52,000 megaton

If it's an icy comet then the density is more like 500 kg/cubic meter, or 1/10th that number.

1040 x more energy that the Tsar Bomba.

Or 5-ish Tsar Bomba per country on Earth.

Or 3466 Hiroshima nukes.

Or 17 Hiroshima nukes per country.

In light of the error in the parent comments math, I retract my previous comment and substitute the following bit of awkward silence:

…

We all make mistakes, as the Dalek said climbing off the dustbin.

FWiW .. here's mine (or is it?)

One Tsar Bomba ~ 50 megatonne. One Hiroshima bomb ~ 15 kilotonne.

One Tsar Bomba ~ 50,000 / 15 ~ 3,333 Hiroshima bombs.

1,040 x Tsar Bomba ~ 3,466,667 Hiroshima bombs.

Oops.

Every time I see your username I can’t help but say it in my mind as Defrost Kelly, some kind of frozen Dr. Leonard "Bones" McCoy

Imagine how I feel every time I see "Dalek" instead of my surname.

90 m/s?

Way too slow, it's more like 70km/s (or 90) - seems you left out a k.

Yes, that was my error - thanks!

I can not confirm this; the parent calculation is the correct one. I can't immediately find what your error was. (edit: It's your [km/s]—you wrote [m/s] by mistake).

    (let* ((ρ ([g (cm -3)] 5))
           (d ([km] 22))
           (m (* ρ (expt d 3)))
           (v ([km (s -1)] 90))
           (ke (* 1/2 m (expt v 2)))
           (kg-tnt ([J (kg -1)] 4.2e6)))
      (values (/ ke kg-tnt)
       (as [megaton] (/ ke kg-tnt))))
    
    5.133857142857142e19 [KG]
    5.133857142857143e10 [MEGATON]

My mistaken use of m/s instead of km/s, in a squared term, indeed gives a HUGE difference.

Thanks!

Based on the corrected 90 km/s instead of m/s it should be 52 pt (peta-ton) impact.

Let's see if I get this math right.

Mauna Loa is about 95,000 km3 in volume says https://www.usgs.gov/volcanoes/mauna-kea/science/geology-and... . Density of TNT is 1.6g/cm3:

  95000 km3 * (1000m/km)**3 * 1600 kg/m3 = ~1.5E17 = 150 pt.

1/3rd of the mountain in TNT.

Nope, I can't conceive of that much energy.

…and after just a few million years to settle down again, we’ll be ready to visit blue sky on Mars!

I would recommend staying on Earth...

Absolutely nothing. Way too small and slow.

How fast does something need to be traveling before you’d consider it to be fast? It probably weighs as much as a city and it is traveling tens of times faster than a high-velocity bullet.

It is of the same caliber as the dinosaur ending meteorite. The planet barely shrugged from it. There is suspicion that something the size of pluto has already hit mars once upon a time. And it is way more massive than this speck of cosmic dust.

Reply on news.ycombinator.com