Hacker News Reader

Comment by jerpint | Hacker News Reader

How does earth get seeded?

Look up ALH-84001. The debate about whether the structures inside this Martian meteorite are fossils is too long for a HN post. But in analyzing the rock it was shown that the during the entire trip from when it was blasted out of Mars to when it fell in Antarctica would have been survivable for rock boring microbes. Not just theoretically, but hard evidence. There are structures that would have been destroyed if the rock was heated enough to sterilize, but they survived the trip. Hundreds of tons of rock like this from Mars land every year.

> Hundreds of tons of rock like this from Mars land every year.

277 total Martian meteorites — with the largest weighing 14.5 kg — is not hundreds of tons yearly.

That's how many have been conclusively classified as Martian out of "the 72,000 meteorites [total] that have been classified". (https://en.wikipedia.org/wiki/Martian_meteorite)

That's obviously not the actual total that have ever made it here.

https://science.nasa.gov/solar-system/meteors-meteorites/fac...

> Scientists estimate that about 48.5 tons (44,000 kilograms) of meteoritic material falls on Earth each day.

That has been going on for billions of years. If the 277/72,000 proportion holds that's a lot of material.

While I recognize your logic, and even mostly agree, the point still stands that it cannot be conclusively and definitively said (as least as far as we've been alive/can tell) that hundreds of tons of Martian meteorites fall to Earth every year. Or even tons at all.

Tons of meteorites in general, sure — but not from Mars.

It is likely given these numbers at least some tons of Martian rock land here annually, which makes the seeding of life concept feasible. I'm on board with "not hundreds of tons", but it's a lot closer estimate than 277 ever.

(48.5 * 365) * (277 / 72,000) = 68 tons per year as an extremely speculative estimate here, ignoring entirely probable variances in what hits us (much of which is sand-grain sized) versus what we identify... and again, any estimate here we have to multiply by a few billion years.

> Scientists estimate that about 48.5 tons (44,000 kilograms) of meteoritic material falls on Earth each day.

Most of it gets destroyed on entry, right? No organic matter surviving?

No, most are smaller rocks and generally decelerate to terminal velocity in the upper atmosphere. It’s the big ones that have too much momentum and penetrate further at speed, causing them to go boom.

The underlying reason is that momentum scales with volume but air resistance scales with surface area.

If there were extra-terrestrial intervention, it would only have needed to be a one-time event.

And it wouldn't be technologically hard to do it such that no trace remains over those timescales.

So, yes, that's "crazy". On the other hand, it's unfalsifiable in the absence of other theories.

There are much saner theories for panspermia.

Like? You're coming across as very dismissive for no reason.

There are meteorites on Earth which very likely originated from Mars. They're believed to have been launched into space by an impact, eventually finding their way onto Earth. If we're looking for the most realistic options for panspermia to have occurred, they'd be due to a natural event of this sort.

It’s very much like how islands in the sea are colonized by life. Some event causes a blob of living creatures to enter the sea on a raft and they drift until they make landfall somewhere else. Sometimes they survive long enough in the new place to reproduce.

Rats leaping from a sinking ship swimming to shore we were.

I'm not arguing against that.

I'm just saying unfalsifiability is a bitch, and it's hard to find hard evidence on geologic timescales.

The burden of proof is on the person making the claim. It is not on someone else to disprove such a claim.

Volcanic eruptions throwing rocks into space. A large impact throwing a huge number of rocks into space.

Reply on news.ycombinator.com