Chicxulub Impact Might Have Spread Life-Bearing Rocks Through the Solar System

KentuckyFC writes "Some 65 million years ago, an asteroid the size of a small city hit the Yucatan Peninsula in what is now Mexico, devastating Earth and triggering the sequence of events that wiped out the dinosaurs. This impact ejected 70 billion kg of Earth rock into space. To carry life around the Solar System, astrobiologists say these rocks must have stayed cool, less than 100 degrees C, and must also be big, more than 3 metres in diameter to protect organisms from radiation in space. Now they have calculated that 20,000 kilograms of this Earth ejecta must have reached Europa, including at least one or two potentially life-bearing rocks. And they say similar amounts must have reached other water-rich moons such as Callisto and Titan. Their conclusion is that if we find life on the moons around Saturn and Jupiter, it could well date from the time of the dinosaurs (or indeed from other similar impacts)."

If we find it, the obvious tests

[JoshuaZ]

At this point, we have a pretty good understanding of using genetics to estimate roughly when two populations diverged. If we find such life, we can first test if it at all resembles Earth life. If it does (in the sense that it uses most of the same amino acids, and uses similar machinery for DNA and replicating DNA), then we should be able to get a rough estimate of when it separated from Earth life based on how genetically different it is. There will be some difficulty with this sort of technique, since the life on alien worlds may be subject to extreme selection pressures, but that should be something we can roughly account for.

Re:And Vise-Versa

[ShanghaiBill]

Liquid water? Check!

Maybe not. Europa is believed to have an ice layer between 10 and 30 km thick [wikipedia.org]. It is unlikely that an impact by a 3m rock would penetrate more than 100m or so. The impact would melt some water, but it would quickly refreeze. Europa's surface is pocked with craters millions of years old, so there does not appear to be a regular turnover of the ice that would carry any surviving life to the ocean below.

Table 5

[ZombieBraintrust]

The 20,000kg number is from Table 5 in the journal. I think the summary is a little deceptive.
Probablilty of life bearing rock ejected from earth reaches Europa is: 2.8E-6 ± 5.0E-7 %
Yeah thats .0000028% plus or minus .0000005%
Including all rocks that were ejected they believe 6 plus or minus .9 rocks would reach Europa.
The 20,000 Kg number comes from those 5 to 7 rocks.

Re:And Vise-Versa

[Samantha Wright]

It's pretty problematic that the impact in question happened in Mexico. The Yucatan isn't exactly a haven of extremophiles—you wouldn't expect to find anything that can maintain a biosphere without a good light source, and they're definitely not well-adapted to the sulphur and magnesium contamination [nasa.gov] that Europa appears to have. Unfortunately the best places to find organisms with a chance of surviving in this kind of environment are at the bottom of the ocean, which is a particularly bad target for producing ejecta. Caves are also a possibility, and since Mexico has no shortage of them, they might be a potential avenue... but who knows if there were any decent ones in the Yucatan at the time.

Re:And Vise-Versa

[ShanghaiBill]

The Yucatan isn't exactly a haven of extremophiles

There are extremophiles everywhere if you go deep enough. Endoliths [wikipedia.org] (organisms that live inside rocks) have been found at depths of 3 km, and probably commonly live even deeper. Endoliths can endure temperatures of 120C (250F), and have also been found in the extreme cold and low humidity of the Dry Valleys of Antarctica [wikipedia.org]. If anything can survive the journey to Europa, it is probably an Endolith.