SKY_September2014.pdf

22 September 2014 sky & telescope

Winged Time Traveler

planetary scientists expected to fi nd widespread carbonate

deposits on Mars. But they haven’t.

Plus, although Mars possesses vast water-ice deposits

beneath its surface, deuterium levels suggest that the

planet has lost roughly 70% of its water.

If the atmosphere isn’t hiding underground, then

some of it must have been lost to space. Gas can escape

if it’s hot enough or if it’s stripped off by the blustery

solar wind. Thermal escape in particular favors the loss

of lighter molecules, because at a given temperature

a lighter molecule zips around faster than a heavier,

tortoise-like molecule.

Losing so much atmosphere would have left Mars

much colder and drier. Liquid water wouldn’t have

lasted on the surface. Geological features suggest that

Mars transitioned from warm and wet to cold and dry

by roughly 3 billion years ago. But scientists don’t know

exactly how long it took for the planet to lose most of its

atmosphere or why. That’s why they built MAVEN.

The Chronologists’ Tools

MAVEN’s time-travel abilities are limited: it won’t fl ash

back 4 billion years to watch the planet’s envelope dwindle

MAVEN’s Science Instruments

Remote Sensing Package IUVS

Imaging Ultraviolet

Spectrometer

Mass Spectrometry NGIMS

Instrument^ Neutral Gas & Ion Mass

Spectrometer

Particles & Fields Package SEP

Solar Energetic Particles

S TATIC

SupraThermal & Thermal

Ion Composition

SWEA

Solar Wind Electron Analyzer

SWIA

Solar Wind Ion Analyzer

LPW

Langmuir Probe & Waves

MAG

Magnetometer

Studies

ionospheric/

atmospheric

profiles

LPW

STATIC

NGIMS

IUVS Limb

Scans

Continuously

measures non-thermal

ions and electrons, magnetic field

Electric Field

LPW Line of solar occultation

Line of solar occultation

STATIC

monitors

escape

IUVS

coronal

scans

IUVS

Atmosphere

disk maps

Measures extreme Pileup of solar magnetic field

UV continuously

when in sunlight

SWIA

STATIC

SWEA

SEP

MAG

Solar

Wind

Above: The MAVEN spacecraft will follow an elongated orbit

around Mars, dipping down to 150 km (in some places 125 km)

above the surface at its closest and fl ying 6,000 km above at its far-

thest. The orbit precesses in both latitude and local solar time so

that scientists can study as much of near-Mars space as possible.

Shown are the investigations and pertinent instruments involved

for various parts of the spacecraft’s orbit.

Left: Technicians pack up the MAVEN orbiter in its launch cone.

Once wrapped up, the complete package sat on top of an Atlas V

rocket for launch (see page 26).

NASA / GSFC / SSLSolar Wind Electron Analyzer

NASA / KIM SHIFLETT

S&T

: LEAH TISCIONE, SOURCE: MAVEN TEAM

Maven_at_Mars.indd 22 6/23/14 12:17 PM