Fields

Fields

Goals of GRACE

GRACE was launched in March 2002 and has a very important mission to deliver. The information gathered from the GRACE mission will reveal the broad features of the Earth’s gravitational field overland and sea. GRACE is sensitive enough to detect small variations and produce detailed maps.

The new gravity measurements will benefit many important applications. These applications include the following:

• understanding atmosphere-ocean mass exchange;

• measuring the changing mass of polar ice caps;

• analyzing changes in water resources on land;

• determining the characteristics of both shallow and deep ocean currents;

• deciphering internal Earth forces that move tectonic plates and result in earthquakes and volcanic;

• grasping the interactions that generate Earth's geomagnetic field; and

• recognizing sea level change resulting from ocean temperature and water mass changes

It will also help to provide more accurate seasonal forecasts for the weather patterns of Earth, an improvement in forecasting of natural hazards, and an ability to track the altering distribution of water resources.

Findings of GRACE

Data from GRACE allowed scientists to conduct the first gravity survey of the entire Antarctic ice sheet. This study found the mass of the ice sheet has decreased significantly from 2002 to 2005.

Canadian and US scientists have been able to use the gravity measurements from GRACE to determine that the ancient ice sheets over Canada were made up of two major ice domes instead of one single massive dome.

Greenland has the largest reservoir of freshwater in the northern hemisphere (second largest on Earth) and any large changes in the mass of the ice sheet will impact ocean circulation, global sea level and climate. The data from GRACE shows that the melting of this ice sheet would add 0.56 millimetres a year to increase sea levels. This information has also been found by independent studies of Greenland’s mass, but in the case they provide a direct measure of ice-mass changes.

These are just some of the many findings GRACE has sent back to Earth.

http://www.nasa.gov/home/hqnews/2006/mar/HQ_06085_arctic_ice.html

http://www.csr.utexas.edu/grace/education/

http://www.engr.utexas.edu/news/articles/200608101082/index.cfm

2. a) Water molecules are attracted to both positive and negative charges because of their polar manner, meaning they have an unequal distribution of election density. The hydrogen end of the molecule is positive and would therefore be attracted to negatively charged atoms such as chlorine in NaCl, whereas the oxygen would be attracted to the positively charged sodium atom. This is illustrated below:

b) Static electricity is produced by charges gathering on an object or body and is usually stimulated by friction. Air can have high conductivity or low conductivity depending on the humidity due to hydrogen bonding. The hydrogen’s on one water molecule are attracted to the oxygen of another molecule. If the humidity level is high there is a great deal of hydrogen bonding and the air’s electrical resistance is low, allowing static charges to be attracted to an oppositely charged body. When the air is dry, it is not as conductive and due to the lack of water vapour and the static charges stay where the build up and you get a shock every time you touch something. Therefore humidity helps to remove excess charges from objects because the water molecules in the air can bond to the excess charges reducing the amount of charge on the object, and also reducing the risk of static shock.

c) Raindrops grow through three processes: nucleation, condensation (where water vapour collects on the nucleated drop) and collection (where falling raindrops bump into other drops and grow). Dust particles and ions present in the air are nucleation centers of water drops.