 The arrival of the Dragon spacecraft has brought much new science to the International Space Station, including a whole new group of Mousetronauts. Two weeks ago, I asked you what your favorite experiment was on the International Space Station, so this week we'll also be talking about the Seedling Growth Experiment. This is your space pod for April 22, 2015. On April 14, SpaceX launched their Dragon capsule as part of their sixth commercial resupply mission. On board were 20 mice destined to be used for bone density research, immune system research, and a study on intracranial pressure. In space, astronauts suffer bone loss and symptoms similar to elderly people here on Earth. Space mice suffer bone loss faster than astronauts, making them a good model for studying this problem. A new bone density testing device, or bone densiometer, will be used on these mice. It is the size of a microwave oven and will use low energy X-rays to determine bone density, muscle and fat levels in a single mouse in as little as three minutes. This will allow more studies of rodent bone loss in shorter amounts of time, paving the way to test new treatments that could reverse and halt the process of bone loss in astronauts and potentially even people suffering osteoporosis here on Earth. These mice will also be used to study the immune system. Mice will be injected with a tetanus vaccine to see how their immune system reacts. Previous research has shown that the immune system is weakened in space. Some of the mice will also receive a compound known to boost the immune system called an adjuvant. Hopefully, the mice that receive both the adjuvant and the vaccine will show a reduction in the negative effects of space flight on the immune system. Every animal flown in space is a precious wealth of potential scientific discovery, so sometimes multiple studies are conducted on the same animals. In the case of the immune system study, these mice will also be used to see changes in intracranial pressure and the resulting effects on the brain. On Earth, gravity acts to pull the fluid in our body down towards our legs, but in space the fluid is free to move around the body and this can lead to an increase in cranial pressure. It is believed that this fluid shift and the increase in cranial pressure can be a cause of some of the vision problems experienced by astronauts. At the end of the immune system study, the space mice will be euthanized and their blood, spleen and liver samples will be frozen for analysis and their brain samples will also be frozen as part of the intracranial pressure study. I previously asked what space station research you'd like to know more about and YouTube user Chris Marshall left a comment asking about plant growth research in space, so I'm going to talk about the seedling growth experiment. The seedling growth experiment launched aboard SpaceX's fourth commercial resupply mission. This experiment studied the growth of the plant Arabidopsis thaliana in microgravity. Arabidopsis seeds were grown under conditions of different gravity and light. The researchers were particularly interested in the direction of plant growth in response to red and blue light. Here on Earth, plant shoots and sprouts mostly grow towards light and you can demonstrate this yourself by taking a potato that has sprouted and placing it in a closed shoe box with a hole poked in one end. Over time the potato shoots will grow towards the light. In microgravity however, plant responses to light can differ. We know that on Earth plant roots tend to grow away from blue light and that the effect is even stronger in microgravity. The cool thing about this experiment though is that the researchers didn't just compare roots growing in 1g to roots growing in 0g, they used centrifuges to simulate Mars gravity as well as moon gravity and guess what they found? The plant roots that they grew in Mars gravity were more similar to those grown in Earth gravity than those grown in 0g. This tends to suggest that the gravity on Mars might be sufficient enough to plants to grow normally. However, this experiment only looked at seeds that were grown up to 7 days old so we have a long road of research ahead of us before we'll be snacking on Mars grown salad. However, I volunteer to be the first to try it. Thank you for watching and for more information about today's topic and relevant references check out the description below. I'd love to give a huge shout out to all our patrons of tomorrow that helped to crowd fund this space pod. Thank you for your contribution and let me know what space topics and space experiments you'd like me to talk about by leaving a comment or via social media. If you'd like more information about how you can help to crowd fund these space pods head over to patreon.com slash space pod and don't forget to check out all our other space pods that cover a wide range of awesome space topics. You'll find them at youtube.com slash T-M-R-O. My name is Lisa Stodzianowski and I'll see you next week where we'll be talking about more cool research happening in space.