[00:00.00]Listen to part of the lecture in an astronomy class.
[00:04.25]Professor: OK. Here's an interesting word, astrobiology. [00:08.69]Have you come across the term astrobiology before?
[00:13.19]Male Student: It sounds like a cross between biology and astronomy.
[00:17.33]Professor: Yes.
[00:18.30]Male Student: So the study of life, astro, stars, space. [00:24.22]So something to do with studying life in space?
[00:28.04]Professor: Yes, precisely. [00:30.10]It's a relatively new science on the margins for a while, but it has now reached respectability, has aspects of biology, astronomy, geology. [00:43.36]But, maybe it's also philosophy. [00:46.51]I mean we're dealing with the unknown, making assumptions, speculations, which well some think this goes a little beyond the usual role of science. [00:57.19]But anyway, one thing we're doing in astrobiology is that we're looking very carefully at microbes. [01:05.16]Bacteria are one example of microbes. [01:08.49]They are tiny organisms. [01:10.82]You need a microscope to see them. [01:11.93]So astrobiologists are interested in whether microbes might have been carried to earth on rocks from other planets. [01:19.62]And studies of a meteorite found in Antarctica seem to suggest that possibility, but it's not just microbes from other planets traveling to earth that scientists are studying. [01:33.60]Going in the other direction, they're looking at whether microbes from earth might have been carried to other planets.
[01:41.35]Student: So could life that traveled from here exist somewhere else?
[01:45.48]Professor: Yes. That's what's fascinating about this. [01:48.92]But first, we better back up a bit. [01:52.45]How could this happen? Microbes going from one planet to another. [01:56.90]One possibility is from the impact of asteroids and comets on planets. [02:03.08]When these objects hit a planet's surface, they form a crater, a hole, and material rocks get ejected from that crater and thrown up into the planet's atmosphere. [02:15.26]Some of the rocks might even escape the planet's gravity and go into outer space.
[02:20.89]Ok. Most of the life in the ejected rocks would die due to extremely high pressures and the high speed of the rocks as to being thrown into space. [02:31.16]But if the living organism was inside a rock on the surface of the planet, but not right where the asteroid hit, there wouldn't be as much pressure on the rock and the organism might survive when the rock gets ejected into space. [02:47.62]Then there's the question of survival in space. Yes?
[02:52.64]Female Student: I don't see how that could happen. [02:54.82]I thought anything living would die in outer space.
[02:57.85]Male Student: There's no air, no food.
[02:59.55]Professor: Yes and there's extreme temperatures, cosmic rays, ultraviolet radiation, but experiments involving bacteria in space have shown that they can survive these conditions. [03:12.29]If a microbe is deep enough inside a rock, it'll be protected from ultraviolet light, which is particularly deadly. [03:19.83]Also, if a microbe forms a spore, it has an even better chance of survival. [03:26.79]I should explain that a spore is a dormant structure formed by some organisms for reproduction or to help in survival. [03:35.38]They have a protective coating to help resist harsh environments, and they have only one or a few cells. [03:43.09]Cold temperatures actually seem to help spores survive. [03:46.60]So a microbe that has developed a spore might even survive in rocks for millions of years.
[03:54.03]Okay? So imagine rocks being thrown up into space because of an impact on a planet in our own solar system, these rocks, some of which might carry organisms, might eventually encounter another planet. [04:09.85]Now, could they survive the entry into the planet's atmosphere? [04:14.50]When the, the rock gets heated from friction with the atmosphere? [04:19.52]If the rock is big enough, the temperature inside it will remain relatively low. [04:24.99]And microbes might be able to survive. [04:28.36]But then there's the impact on the planet's surface. [04:31.49]There it helps if the rock is smaller. [04:34.57]If that same large rock with microbes in, it shatters in the atmosphere, then these smaller pieces would hit the surface with less force than if the rock state intact and microbes might survive.
[04:48.64]Male Student: What about microbes traveling on spacecraft? [04:51.43]Like a space probe sent to Mars, could they carry microbes?
[04:54.70]Professor: Well, let's look at the space probe Galileo, which was sent on a mission to Europa, one of Jupiter’s moons. [05:01.91]It, well, Europa seems to have an ocean of water just below its icy surface, and it might be capable of supporting life. [05:11.11]The people in charge of the Galileo mission didn't want to probe to crash into Europa and contaminated with microbes from earth that it might have been carrying. [05:19.80]So at the end of the mission, they steered Galileo toward Jupiter atmosphere, where it burned up.
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