Ebb and Flow

GRAIL A and B are lunar satellites launch by NASA that will be studying the gravitational field of the Moon (see GRAIL). The spacecrafts just arrived at the moon on December 31st 2011 and January 1st 2012. To get the general public involved in the mission, NASA decided to hold a competition for elementary school students in which they proposed new, more creative names for GRAIL A and B. The winners are a class of fourth grade students from Montana, who came up with the names "Ebb" and "Flow". Ebb means to move back or away (like a receding tide), where as flow means to move forward, like a flowing stream. The Moon's gravity is what causes the tides to occur, and since GRAILS primary mission is to study the Moon's gravity and how it affects Earth, these names are quite appropriate. Keep an eye out for other space related competitions that you can participate in on the NASA website: www. NASA.gov

Image Credit: NASA

GRAIL

Artists impression of GRAIL

Even though the space shuttle program has ceased, NASA is still alive and active with eyes towards the moon. On Saturday, September 10th around 9am EST, NASA launched the Gravity Recovery and Interior Laboratory (GRAIL) spacecraft from Cape Canaveral, FL. GRAIL is a set of two satellites that will orbit the moon and map its gravitational field. The moon has about 15% the amount of gravity we experience here on Earth, mainly because it is only about a quarter of the size of Earth. Understanding the moons gravitational field will help scientists understand the moons interior structure reconstruct its past. We will be able to answer questions like: Does the moon have a molten core? Why do the craters on the light side of the moon appear to be filled with solid magma, while those on the dark side do not? One interesting thing about the launch of GRAIL is its journey to the moon. A trip to the moon for the space shuttle took about 3 days, but GRAIL is going to take 3.5 months! The rocket was actually aimed in the direction of the sun, and with the help of small thrusters the trajectory will be corrected so that the satellites will reach the moon. This is called a low-energy trajectory and was done intentionally to save fuel, and to leave time for the satellites and equipment to adjust for space conditions. Think about it like this: if we hurtle towards the moon in three days, it will take a lot of fuel and energy to slow the satellites descent so they don't crash into the moon. But if instead we go the "long way around" and leisurely approach the moon, we can just float into orbit using very little fuel only to adjust trajectory. In these hard economic times, NASA is trying to save every penny they can!

Image credit: NASA/JPL/MIT