A Martian fossil? This and similar objects were once promoted as remains of bacteria in a meteorite from Mars. The idea is not widely believed today, but still has some supporters. (LPI/NASA image)
Lecture 10
A Martian fossil? This and similar objects were once promoted as remains of bacteria in a meteorite from Mars. The idea is not widely believed today, but still has some supporters. (LPI/NASA image)
Life in Space
This is a big subject! We can split it into three parts:
1. Human survival in space (what can we do in space, and what effects does space have on us?)
2. 'Alien' life in our solar system (does it, or could it, exist? How should we treat it if it does exist?)
3. Life throughout the universe. (This is the topic for our next lecture.)
Humans in space.
It is expensive and difficult to put people into space. A 300 kg machine can do a lot, but 300 kg is not much mass if we have to include a person and all the equipment needed for survival, including air, water, temperature control and food. Also, people need more reliable equipment than robots, because the implications of a failure are different. Finally, people have to come back, so heavy and expensive return systems are needed. On the other hand, robots are still slow and indecisive - witness the rovers on Mars, great as robots go but incredibly slow and fragile. A human geologist could have done in a day what one rover did in a year.Thus there has been a big debate about the need for people in space ever since the first astronauts flew in 1961. It it still going on today.
The case against human spaceflight
Robots or people? - both!
Space medicine
Space affects people in several ways. The lack of gravity affects balance and blood flow. It reduces loads on bones, which seems to stop them absorbing calcium from food, so bones weaken over long periods. Blood, no longer pulled down by gravity, redistributes itself in the upper body and head. The heart and other muscles don't have to work so hard and become weaker, requiring extra exercise to stay strong. Radiation is a problem outside the Earth's radiation belts, or over long periods in orbit. And of course people have to be kept within reasonable temperature and pressure ranges. The Apollo 1 crew died because their spacecraft, during a ground test, was filled with pure oxygen to reduce internal pressure while still leaving enough oxygen for the crew. The oxygen plus a stray spark from frayed electrical insulation caused a fire with disastrous results. As a result, modern spacecraft atmospheres include nitrogen and are at regular Earth surface pressure, but space suits are operated at lower pressure so they will not puff up like balloons or become too rigid. This means that special procedures are needed to avoid pressure-change illness ("the bends") during spacewalks. Astronauts prepare for an EVA (extra-vehicular activity, = spacewalk) by being isolated to slowly adjust to the changes in pressure. So medical issues are very important in human spaceflight. And consider this: how would you deal with a medical emergency during a 2 year mission to Mars? Is surgery possible in zero gravity? People are studying it now.
Apollo 1
Space medicine
Space medicine
Medical problems of long duration spaceflight
Space medicine studies in Canada
Natural resources in space
If we want to live in space, or on the Moon or Mars, what resources can we find and use to help us? Lifting things off Earth is difficult and expensive, so using resources we find locally might save time and money. Energy is one important area - sunlight can produce electrical power if we are in the inner solar system, but it's more difficult to use by the time we get past Jupiter. (Small nuclear generators are used on outer planet spacecraft like Voyager and Cassini, or for use at night, such as on the Viking landers on Mars. On the Curiosity rover a small nuclear generator is used to recharge the batteries the rover runs off, and to keep warm at night). We might even beam electricity to Earth from orbit or the Moon. On the Moon, raw soil could be used for radiation shielding (over buried habitats, or as berms around nuclear generators). That soil could be processed to make oxygen and iron, aluminum or titanium, or it could be melted and cast into bricks or spun into fibreglass. Hydrogen might be obtained in small quantities from lunar soil, or large quantities from ice found in permanent shadows near the pole. Asteroids might offer the same resources, and some may contain carbon compounds for more complex manufacturing. 3D printing (additive maufacturing) will make all these things easier and may revolutionize space exploitation in future. Mars offers carbon dioxide, and water from buried ice or in the soil. Comets can also provide water. Finding and using resources in space (= in situ resource utilization, ISRU) will be difficult, but it will be investigated during future Moon or Mars activities.
space resources
resources and legal issues
resources and legal issues
Lunar resources
Natural hazards in space
Space contains resources, but also hazards than can interfere with life and activity in space. Radiation is a major threat - both particles and electromagnetic waves like X-rays. In Low Earth Orbit we are protected by Earth's magnetic field. On the Moon, or on the way to Mars, shielding will be essential. A lunar habitat might be covered over with regolith (= lunar soil). Electrostatic shields have been considered, as well as building a base in a natural magnetic shield. Designers are considering building safe areas in Mars-bound spacecraft, small rooms surrounded by all the supplies, food and water needed on the journey. Meteoroids - little rocks, even gravel-sized, travelling at very high speed could hurt or kill an astronaut, but pieces large enough to do this are very rare. In Low Earth Orbit there is enough loose junk floating around that it has to be tracked carefully, and the Space Shuttle or the Space Station can be maneuvered out of harm's way when needed. Other future hazards include fine dust on planetary surfaces. Dust was a nuisance for Apollo astronauts and will be on Mars as well, infiltrating habitats and clogging and degrading machinery. Will it be toxic, or cause allergies, if we breathe it in over long periods?
Radiation hazards
Radiation and Space Tourism
Radiation
Radiation
Radiation protection on the Moon
Radiation protection on the Moon (and other aspects of lunar architecture)
Space debris
Space debris
Lunar dust hazard
Natural hazards from space
We should also consider hazards from space that affect us on Earth. We can't escape space hazards by abandoning space exploration. Radiation - solar flares - can knock out power grids on Earth (Quebec in 1994), and a gamma ray burst in the solar neighbourhood could potentially fry half the planet and cause long-term climate change. Asteroids and comets can hit Earth - look at craters on Earth for evidence - and we think they can cause enough climate change to kill many species. The dinosaurs may have met this fate. Only now are we approaching the ability to deflect approaching asteroids. Some have argued that impacts will inevitably wipe out any planetary civilization over long periods, and the only (very) long term solution is to spread civilization among multiple planets to guarantee survival.
Recent solar flare
Solar flare effects
Impact effects
Impact effects
Impact craters
asteroid deflection
Gamma Ray bursts.
Life in the solar system?
People used to say that life needed warmth, air and water - in other words, a place like Earth. The notion arose of a 'habitable zone' around a star: too close is too hot, too far away is too cold. Within a certain zone conditions are comfortable. In our solar system only Venus, Earth and Mars would be in this zone, and Venus and Mars are marginal. We now see this is too narrow a definition. First, we find life in unexpected places on Earth: hot springs, ocean floor volcanic vents, deep in the Earth's crust, under ice in Antarctic lakes, even in nuclear reactors. Life can cope with a wider range of conditions than we thought, especially bacteria. Then it began to seem that these extreme bacteria might be the oldest types of life on Earth, the very origin of life itself. Now we have evidence of water in the Martian crust, an ocean on Europa, a moon of Jupiter, and hot water vents on Enceladus, a moon of Saturn. Could life exist elsewhere? Could we change a sterile world to make it habitable (= Terraforming)? Astronomers have also defined a habitable zone in our galaxy - near the centre of the galaxy, stars are close together and the giant black hole in the centre of the galaxy produces strong radiation. Conditions may be too hazardous for life to thrive. Further out - where we are - conditions are more stable and living things can thrive.
Origin of life.
Galactic habitable zone?
Habitable zone.
Habitable zone.
Land and water planets.
Terraforming.
Terraforming.
Planetary contamination
If life does exist elsewhere, can we keep it safe from us, and us safe from it? Apollo astronauts on the earlier moon landing missions had to spend time in a quarantine facility after their return. This was a waste of time - the Moon is sterile and the quarantine was far too loose to be of any use - but it was really done for public relations purposes. Mars will be a different story. If we land people it will be impossible to stop us 'infecting' Mars with bacteria. We may have done so already with our robots. If people or soil are returned to Earth, any Martian organisms may hitch a ride back with them. These acts are called Forward Contamination (we infect another planet) and Back Contamination (we bring something dangerous back to Earth). Meteorites have already crossed between Mars and Earth - the two planets might 'infect' each other without our help. If life exists elsewhere in the solar system, can it travel between worlds on meteorites? This idea is called 'panspermia'. Recent experiment showed that lichens and a strange kind of invertebrate aminal called a tardigrade can survive exposure to space conditions (vacuum, radiation, temperature extremes) for relatively short periods. How about 'biosphere reserves' - should we protect Martian life, if we discover it, by not going there again? Would Martian bacteria have a right not to be affected by terrestrial bacteria?
Apollo quarantine
Mars contamination
Lichens survive space conditions.
Invertebrates survive space conditions.
planetary contamination (PDF file)
Forward and back contamination
Forward and back contamination
Cleaning up after ourselves?
Panspermia
A Martian fossil? This and similar objects were once promoted as remains of bacteria in a meteorite from Mars. The idea is not widely believed today, but still has some supporters. (LPI/NASA image)