A very hungry caterpillar

Monday 8 June 2015

Last week a student of mine began experimenting with some lettuce plants as part of an extended essay to evaluate their suitability for a space mission to Mars. We were astonished to see that students from University of Southampton Spaceflight Society, studying a range of subjects from Biological Sciences to Engineering had won a competition for some payload space on a Mars One mission to grow lettuce on Mars.

Mars One is a not for profit foundation with the goal of establishing a permanent human settlement on Mars. To prepare for this settlement the first unmanned mission is scheduled to depart in 2020. Crews will depart for their one-way journey to Mars starting in 2026

Why did they choose Lettuce? Every time we try to grow some in the lab we have problems. Is it really feasible to grow them on mars, will they produce more oxygen than algae like Spirulina, the favoured plant of the European Space Agency? Time will tell, but for now let's get back to the lettuce in my biology lab.

We left them in an aquarium over the weekend with lid on, to keep moisture in as the weather was over 30°C all weekend. On Monday morning disaster struck, the plants had been ravaged by something and were close to death.

It took just a few moments to identify a large green caterpillar on the side of the glass.  I wish I'd taken a photo, but I didn't anticipate the caterpillar's next moves. Over the next hour it made a silk cocoon around itself and turned black.

By a lucky chance I'm teaching about insect life cycles in a Forensic science topic in the middle school this week but this is also a great piece of qualitative data for my student's extended essay.  Luckily we have some other lettuce plants for him to use.

It made me think I could make more of this type of project.  A small bunch of grapes, or an old banana in a sealed aquarium will see fruit flies hatch out after just a few days. If you don't want to use them for forensic science then they might be useful for genetics studies.

As my student pointed out, "there is less chance of a caterpillar hatching out on the surface of Mars", so maybe the Southampton students won't have to worry.  If caterpillar eggs won't survive the journey to mars how will the lettuce seeds, don't they respire even while they are dormant?


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