Making a Mini Mars for Testing Probes
Meera - This week I've come down to the labs of the Planetary and Space Sciences Research Institute at the Open University in Milton Keynes. It's not your average kind of lab as there isn't a white bench or a white coat in sight. There are large metal vessels all over the room with circular windows basically looking like mini space ships all over the place. I'm here with Martin Towner who's a research fellow here at the Open University. He's going to tell me what these vessels are really here for.
Martin - These chambers all get used to simulate conditions on other planets in the solar system. This particular area is mainly to do with the testing and building of instruments. We have a whole bunch of different areas to simulate the environments that space craft have to go through on their way to get to Mars or to get to Titan and to land and survive for a period of time. The majority of our work is simulating the Mars conditions for upcoming future missions.
Meera - What is the environment like on Mars?
Martin - Mars is very different from the Earth. The atmosphere is a lot thinner than Earth's and is also CO2, carbon dioxide rather than oxygen and nitrogen like we have here. It's also a lot colder and a nice sunny day on the equator on Mars might get up to just above freezing. Whereas a cold winter night time you might be talking -120C. The sunlight is also very different. Mars is farther from the Earth so the light is a bit dimmer but it's also a lot harsher because there's no ozone layer around Mars. You have strong UV, ultra violet on the surface. On Earth the burn time of our day is half an hour where as on Mars you're talking a couple of minutes.
Meera - That's a big difference.
Martin - It would probably be the least of your worries if you were on the surface. The ultraviolet is so strong that it effectively sterilises the surface of the planet.
Meera - How do you know that these are definitely the conditions?
Martin - In most of the cases they've actually been measured. There have been space craft that have landed on Mars, they've measured the temperature, the wind speed, the air pressure. We actually have data for that. There are big climate models in the same way that people do climate modelling on the Earth. People do climate models for Mars as well so the global conditions are understood. Things like the ultraviolet fluxes are well known but can be modelled because you know the composition of the atmosphere. You know how far away from the sun you are so you can work out all these things.
Meera - We've got out all these chambers here in which you tried to recreate these conditions. How'd you go about doing that?
Martin - Because of the low pressure on Mars you have to have a big metal chamber that you can take the air out of and then fill it with a Mars atmosphere. You have a big pump connected to a big metal chamber and this one is about 2m long and about 1m diameter. Pump all the air out. Fill it with a bit of carbon dioxide, which gives us the atmosphere. We have a bunch of big lamps which can be switched on and off by computer to give us the day-night cycle. The Mars day is slightly longer than the Earth day.
Meera - What kind of lamps?
Martin - Ultraviolet lamps and then also a normal light bulb type lamp that gives us the visible spectrum as well as the ultraviolet. We need both. Temperature is done using liquid nitrogen through a big copper plate. Liquid nitrogen will get us down to below -150 which covers the worst case on Mars. Then we can control that to bring it up and down to do the day-night cycle or to simulate different areas of Mars: equator, North Pole, South Pole. Things like that.
Meera - Do you put all of these conditions in each chamber in one go or do you look at different things in each chamber?
Martin - No, the chambers tend to be specialised for people studying astrobiology like life on Mars. They want a small, nice clean chamber. They may not be interested in the light. They might just want it cold and dark because they're studying things that are underground. Whereas if someone is doing more physical processes like wind and sand blowing around they may want a great big chamber so that the air has got space to move. They might not be too interested in getting the absolute coldest temperatures because things like wind-blown sand is not really dependent on whether it's -20 or -50.
Meera - Why is it important? What kind of effects do these conditions have on the instruments in the first place for you to have to study this so much?
Martin - Mainly it's the temperature, especially when it gets very cold at night and then a little bit warmer during the day. You repeat this day after day after day and it just starts to have wear and tear on the instrument: on the joint, on the soldering and the electronic components in the instruments and also things like the battery as well. You also have to be very careful with the lighting. Things like plastics tend to degrade under strong ultraviolet conditions.
Meera - How do you overcome this?
Martin - It's the old adage of test, test and test again. You have to pick the right materials so that they don't crack or fade or bend or just creep slowly under these conditions. This also effects the accuracy of the instrument as well which you have to measure so that somebody knows their instrument works equally well at -60 as it does at -20 in the middle of the day or the middle of the night. You just have to work your way through all the different combinations of instruments and environment conditions and then weed out anything that doesn't make the grade and replace it with maybe a better material or a better design.
Meera - Survival of the fittest?
Martin - Yes, basically.
Meera - Is there nowhere on Earth you could go to try and get these conditions naturally?
Martin - There are some places that are close. The Antarctic dry valleys are the ones that people traditionally use. It's very cold, very dry. Because of the conditions you get a strong ultraviolet from the sun but you don't get the right atmosphere. You're still trapped in the Earth's atmosphere and at a practical level doing fieldwork to Antarctica and taking all your instruments out there is actually a lot more expensive than building a chamber in the lab and testing here.