"My question is about the pictures taken on mars. Why does NASA change the coloring throughout the pictures to make them look red?"
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Question
Do we know how evolution of internal and external biological systems might change in different gravitational environments?
Not yet. We are just beginning to understand the present changes in our own biology in different gravitational environments; at this point it would be hard to predict how evolution might change course in different gravities. However, much study is being done in the related field of developmental biology. We study hypergravity in these systems (greater than 1 G, earth’s gravity) mainly with centrifuges. Conversely, we study hypogravity (< 1G) with water immersion, suspension devices, bedrest, and animal experiments done on shuttle missions. Frogs, rats, plants, and fruitflies are among the organisms studied in developmental biology experiments in microgravity. To read about how gravity affects animal development, see http://astrobiology.arc.nasa.gov/workshop/speakers/wolgemuth/wolgemuth_abstract.html
Microgravity affects almost every part of an organism subject to loading (term used for application of a gravitational force): cardiovascular, neurovestibular, and musculoskeletal systems, to name a few. In the context of evolution, snakes and giraffes are good animals to study, because they have evolved comparable biological mechanisms for counteracting cardiovascular challenges of gravity. For example, aquatic snakes have hearts roughly in the middle of their bodies, because they spend their time in water, where gravity exerts the same force over their entire bodies. Arboreal snakes, however, have hearts much closer to their heads in order to facilitate blood moving upward against the gravitational force applied when they ascend trees. Giraffes, on the other hand, have thicker blood vessels in their feet in order to keep the extensions from swelling with blood (blood pressure is greater than twice human BP at heart level). They also have very elastic blood vessels in their heads and necks in order to handle changes in blood pressure due to head swings.
For a thought provoking discussion on gravity’s function and its role in evolution, please see Dr. Emily Holton’s presentation, "Gravity and Biology," at http://nai.arc.nasa.gov/index.cfm?page=farchive
October 29, 2001
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