Header Bar Graphic
Astronaut ImageArchives HeaderBoy Image
Spacer

TabHomepage ButtonWhat is NASA Quest ButtonSpacerCalendar of Events ButtonWhat is an Event ButtonHow do I Participate Button
SpacerBios and Journals ButtonSpacerPics, Flicks and Facts ButtonArchived Events ButtonQ and A ButtonNews Button
SpacerEducators and Parents ButtonSpacer
Highlight Graphic
Sitemap ButtonSearch ButtonContact Button

 
LFM banner


Mars Glossary

A-B-C-D- E-F-G-H- I-J-K-L- M-N-O-P- Q-R-S-T- U-V-W-X- Y-Z

- - A - -

aerobraking

the use of atmospheric drag to slow a spacecraft

albedo

a measure of the ability of a body to reflect light

aphelion

the point in the orbit of a planet where it is farthest from the sun

astronomical unit (A.U.)

a measure for distances within the solar system, equal to the mean ditance of the Earth from the sun, which is about 93,000,000 miles

atmosphere

the gaseous envelope surrounding a celestial body

axis of rotation

the straight line, real or imaginary, passing through a rotating body and is the line about which that body rotates

azimuth

the distance in degrees along the horizon, westward from the south point of the horizon, to the place where a vertical circle through the star or other object intersects the horizon

- - B - -

backscattering

the deflection of particles or radiation by scattering processes through angles greater than 90 degrees with respect to the original direction of motion

black body

an ideal or imaginary body that is absolutely black when cold, but is a perfect absorber of radiation and at the same time a perfect radiator. Black body temperatures are used to work out the theoretical laws of radiation and to calculate the temperature of the sun.

- - C - -

carbon dioxide

a gas used by all green plants and recycled by them to form wood and the oxygen we breathe. In very large quantities it can be poisonous to animal life.

CCD

charge coupled device

celestial equator

the great circle of the celestial sphere all points of which are 90 degrees from the poles. It is the plane of the Earth's equator projected onto the celestial sphere.

climatology

the scientific study of climate

convection

transmission of heat by moving heated gases. In a hot-air furnace the heated air rises and cooler, heavier air falls.

- - D - -

density

the amount of matter in a unit volume of a substance; usually the mass per unit of volume

diameter

the distance from one side of a body to the other, measured through the center

diurnal motion

the apparent daily rotation of the heavens from east to west; an effect of Earth's rotation about its axis

- - E - -

eccentricity

the degree of flattening of an ellipse and how much it deviates from a circular shape. With reference to the orbit of a planet, the distance between the center of its orbit and the center of the primary about which it revolves.

escape velocity

the speed that any object must acquire in order to escape from a planet's gravitation

- - F - -

fluorescence

the emission of electromagnetic radiation as the result of exposure to some other radiation, which emission ceases when the stimulus that produces it ceases to act on the emitting substance. Thus light passing through a gas, may change the energy state of the atoms and cause them to emit light of a different wavelength.

- - G - -

geodetic

the study of the size and shape of Earth, the measurement of terrestrial gravitational forces, and the location of fixed points on Earth's surface

gibbous phase

the phase when more than half (but not all) of the planet's side facing Earth is illuminated by the sun.

- - H - -

hour circle

a great circle of the celestial sphere passing through the celestial poles and a celestial body or the vernal equinox. An hour circle moves with the body as the celestial sphere rotates, unlike the celestial meridian of a point that remains fixed.

- - I - -

interference fringes

the alternate light and dark bands that are seen when two beams of homogenous light enter into interference with each other, i.e., when they overlap and illuminate an identical area

interferometer

any instrument designed for producing and studying interference of two or more trains of waves or beams of electromagnetic radiation of the same range of wavelengths. Usually denotes an optical interferometer that separates a beam of light into two or more parts that travel in different paths and are then combined together to produce interference fringes.

- - J - -

joule

the S.I. unit of energy, work, or quantity of heat. It is the force of one newton acting over a distance of a meter.

- - K - -

Kepler's laws of planetary motions and orbits

Laws governing the motions of planets in their orbits:

1. The orbits of the planets are ellipses with the sun at a common focus.

2. The line joining a planet and the sun sweeps over equal areas during equal intervals of time.

3. The squares of the periods of revolution of any two planets are proportional to the cubes of their mean distances from the sun.

- - L - -

landing rocket

a "secondary rocket" intended to be used for descending to the surface of the moon or another planet while the major vehicle remains in an orbit around the destination body

- - M - -

mass

the amount of matter in a body, which should not be confused with weight. The same object will have different weights in space and Earth but the mass remains constant.

- - N - -

nadir

the point on the celestial sphere that is diametrically opposite the zenith, so that the zenith, nadir and center of Earth are in one straight line. It is always 90 degrees below the horizon.

- - O - -

occultation

the hiding of one heavenly body by another, as when the moon passes between Earth and a star, or when one of the moons of Jupiter or Saturn passes behind the planet

opposition

the point in a planet's orbit in which it is closest to Earth. When viewing a planet it will appear on the opposite side of the sky as the sun. Two bodies are in opposition when the difference in celestial longitude is 180 degrees.

- - P - -

payload

anything that a flight vehicle carries beyond what is required for its operation during flight

primary

(1) A sun with respect to its planets, or a planet with respect to its satellites; (2) the brighter member of a double star system

perihelion

the point in the orbit of a planet where it is nearest to the Sun

- - Q - -

quadrature

two bodies are in quadrature when their difference in celestial longitude is 90 degrees. This is the position of a superior planet when its elongation is 90 degrees, east or west, depending on the direction of the planet from the Sun

- - R - -

retrograde motion

backward (westward) motion of the planet among the stars, resulting from the fact that it is viewed from the moving Earth. It is the motion that a planet has when its right ascension is decreasing.

Each year, when Earth passes a superior planet, such as Mars, the planet appears to move backward for a short time. It is the same effect you see when two trains are running in the same direction on side by side tracks. The slower train appears to be moving backward.

right ascension

a celestial coordinate; it is the angular distance measured from the vernal equinox eastward along the celestial equator to the hour circle of a given star or other celestial body. It can be defined also as the arc of the celestial equator or the angle at the celestial pole between the hour circle of the vernal equinox and the hour circle of the body.

- - S - -

spatial resolution

a measure of a system's ability to control a robot's tool tip

- - T - -

telemeter

1. an instrument that provides its data readout to a location remote from the sensing device;

2. to transmit data to a remote point

telemetry

the use of telemeters for measuring and transmitting data

teleoperation

the remote operation of a device. In the field of telerobotics, robotics and teleoperations are merged to produce a remotely operated robot.

terraforming

transforming a hostile environment into one able to sustain human life; this includes a source of oxygen, water, plant life, and correct air pressure and temperature.

tetrahedral

a solid with four plane faces

topography

the configuration of a land surface, including its relief

- - U - -

ultraviolet radiation

the invisible electromagnetic radiation beyond the violet end of the spectrum of visible light, of wavelengths ranging, roughly, from 4000 down to 400 angstroms

- - V - -

vernal equinox

the position on the celestial sphere occupied by the sun on or about March 21 when its path on the ecliptic crosses the celestial equator going from south to north. This point is also called the March equinox and the First Point of Aries.

- - W - -

winter solstice

the position on the ecliptic occupied by the sun about December 22 when it reaches its greatest southerly declination

- - X - -

x-rays

very short wavelength radiations beyond the ultraviolet in the spectrum, which are about one ten-thousandth as long as the visible violet and are extremely penetrating

- - Y - -

ylem

the hypothetical primordial matter, proposed by George Gamow, from which the chemical elements may have been formed

- - Z - -

zenith

the point of the celestial sphere directly overhead, 90 degrees above the horizon, for any point on Earth; it is the point where a plumb line extended upward would intersect the celestial sphere
**Definitions from the Academic Press Dictionary of Science and Technology and the Dictionary of Astronomy and Astronautics by Spitz and Gaynor.




credits
 
Spacer        

Footer Bar Graphic
SpacerSpace IconAerospace IconAstrobiology IconWomen of NASA IconSpacer
Footer Info