GRAIL Heads to the Moon

Fire and smoke light up a blue sky as a United Launch Alliance Delta II Heavy rocket propels NASA's Gravity Recovery and Interior Laboratory (GRAIL) mission into space. Liftoff from Space Launch Complex 17B on Cape Canaveral Air Force Station in Florida was at 9:08:52 EDT Sept.10.

The spacecraft are embarking on a three-month journey to reach the moon. GRAIL will fly twin spacecraft in tandem around the moon to precisely measure and map variations in the moon's gravitational field. The mission will provide the most accurate global gravity field to date for any planet, including Earth. This detailed information will reveal differences in the density of the moon's crust and mantle and will help answer fundamental questions about the moon's internal structure, thermal evolution, and history of collisions with asteroids. The aim is to map the moon's gravity field so completely that future moon vehicles can safely navigate anywhere on the moon's surface. 

The Moon's North Pole

The Earth's moon has been an endless source of fascination for humanity for thousands of years. When at last Apollo 11 landed on the moon's surface in 1969, the crew found a desolate, lifeless orb, but one which still fascinates scientist and non-scientist alike.

This image of the moon's north polar region was taken by the Lunar Reconnaissance Orbiter Camera, or LROC. One of the primary scientific objectives of LROC is to identify regions of permanent shadow and near-permanent illumination. Since the start of the mission, LROC has acquired thousands of Wide Angle Camera images approaching the north pole. From these images, scientists produced this mosaic, which is composed of 983 images taken over a one month period during northern summer. This mosaic shows the pole when it is best illuminated, regions that are in shadow are candidates for permanent shadow.

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Our Planet and Sun

What causes the sun to vary? 

We live in the extended atmosphere of a magnetic variable star that drives our solar system and sustains life on Earth. Our Sun varies in every way we can observe it. The Sun gives off light in the infrared, visible, ultraviolet, and at x-ray energies, and it gives off magnetic field, bulk plasma (the solar wind) and energetic particles moving up to nearly the speed of light, and all of these emissions vary. These variations occur on timescales from milliseconds to billions of years. Most of these variations are related to the solar magnetic field, which is caused by the moving plasma inside the rotating Sun, which make a dynamo. 

How do the Earth and Heliosphere respond?

Our planet is immersed in this seemingly invisible yet exotic and inherently dangerous environment. Above the protective cocoon of Earth’s lower atmosphere is a plasma soup composed of electrified and magnetized matter entwined with penetrating radiation and energetic particles. The Earth’s magnetic field interacts with the Sun’s outer atmosphere to create this extraordinary environment.

Our Sun’s explosive energy output forms an immense, complex magnetic fields structure. Hugely inflated by the solar wind, this colossal bubble of magnetism known as the heliosphere stretches far beyond the orbit of Pluto, from where it controls the entry of cosmic rays into the solar system. On its way through the Milky Way this extended atmosphere of the Sun affects all planetary bodies in the solar system. It is itself influenced by slowly changing interstellar conditions that in turn can affect Earth’s habitability. In fact, the Sun’s extended atmosphere drives some of the greatest changes in the near-Earth space environment affecting our magnetosphere, atmosphere, ionosphere, and potentially our climate.

What are the impacts on humanity?

Modern society depends heavily on a variety of technologies that are susceptible to the extremes of space weather — severe disturbances of the upper atmosphere and of the near-Earth space environment that are driven by the magnetic activity of the Sun. Strong electrical currents driven in the Earth’s surface during auroral events can disrupt and damage modern electric power grids and may contribute to the corrosion of oil and gas pipelines. Changes in the ionosphere during geomagnetic storms driven by magnetic activity of the Sun interfere with high-frequency radio communications and GPS navigation. During polar cap absorption events caused by solar protons, radio communications can be severely compromised for commercial airliners on transpolar crossing routes. Exposure of spacecraft to energetic particles during solar energetic particle events and radiation belt enhancements can cause temporary operational anomalies, damage critical electronics, degrade solar arrays, and blind optical systems such as imagers and star trackers used on commercial and government satellites.

Harsh conditions in the space environment also pose significant risks for the journey of exploration. Although space is a near-vacuum, the very-thinly-spread particles and fields are like an ocean that can affect the spacecraft and astronauts that travel through it. Like seafaring voyagers, space explorers must be constantly aware of the current space weather and be prepared to handle the most extreme conditions that might be encountered.

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PHASES OF THE MOON

The revolution of the Moon around the Earth causes the Moon to appear to change shape in the sky. These different shapes are called "phases" of the moon. The Moon passes through a cycle of eight phases every 29.5 days. There is no definite starting point for the cycle, but phases follow one behind the other in a strict order. You will find images of each of the eight phases, as well as a breif description of each phase. The images reflect the order the phases are viewed from the earth. 

Waxing Crescent

The visible moon is partly but less than one-half illuminated by direct sunlight while the illuminated part is increasing.
First Quarter

One-half of the moon appears illuminated by direct sunlight while the illuminated part is increasing
Waxing Gibbous

The Moon is less than fully illuminated but greater than half illuminatedby direct sunlight while the illuminated part is increasing
Full Moon

The visible moon is fully illuminated by direct sunlight.
Waning Gibbous

The Moon is less than fully illuminated but greater than half illuminatedby direct sunlight while the illuminated part is decreasing
Last Quarter

One-half of the moon appears illuminated by direct sunlight while the illuminated part is decreasing
Waning Crescent

The visible moon is partly but less than one-half illuminated by direct sunlight while the illuminated part is decreasing.
New Moon

The visible moon is not fully illuminated by direct sunlight.

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