Phoenix 2007 Lander on Mars

Onboard pressure sensor based on Vaisala BAROCAP® technology On May 25th, 2008, NASA’s Phoenix 2007 Lander successfully touched down on Mars’ northern polar region.

The landing site is at 68 degrees north latitude, 233 degrees east longitude, in an area called Scandia and Vastitatis Borealis Marginal. The landing site is above the Martian polar circle. The local season in Mars is currently late spring-early summer. Therefore the Lander is carrying out its 90- to 150-day mission at a time of year with nightless nights. After the summer season, the approaching winter, and decreasing daylight and available energy will mean that operations will have to cease, and contact with the Lander will be lost.

The Phoenix Lander carries a versatile suite of scientific instruments to analyze soil, observe local meteorology and take macro and microscopic images of Mars. The onboard meteorological instrument includes a pressure sensor, based on Vaisala BAROCAP® technology, for atmospheric barometric pressure measurement. This instrument was developed by the Finnish Meteorological Institute.

Phoenix science
The Phoenix mission has three scientific goals:

1. To study each phase of the history of water at the landing site
Geological evidence suggests that liquid water once flowed on Mars and created rivers, lakes and seas. It is assumed that northern lowlands were once covered by sea and the subsurface ice there may be a remnant of that sea. This conclusion is supported by observations made by the Mars Odyssea orbiter’s gamma spectrometer instrument and other satellite data. The water ice content of near-surface material in the northern polar regions may even be over 50%.

This subsurface ice may well be released over a period of millions of years as Mars experiences climate changes due to its wobbling rotation axis. On a shorter time scale, subsurface ice may well “breathe” every day, every season, converting tiny amounts of frost to water vapor and back. In this way, the ice table may slowly rise and recede as the climate changes.

2. To determine whether the arctic soil on Mars could support life
Life as we know it requires liquid water, but it does not necessarily require the continuous presence of this water. Phoenix is investigating the possibility that some of the ice in the soil of the landing site will melt and become biologically available during the warmer parts of long climate cycles. Phoenix is also investigating the possibility that certain organic compounds necessary to life as we understand it are present. However, Phoenix will not be carrying out direct microbiological experiments for detecting life.

3. To study the weather on Mars from the polar perspective
The amount of water vapor in Mars’ polar regions varies significantly from season to season. Winds carrying water vapor can move water from place to place on the planet. Phoenix is monitoring temperature, pressure, winds, atmospheric dust, ice particles and clouds. These observations will help to increase the understanding of atmospheric dynamics and interaction between polarand mid-latitudes. The circulation of volatiles (H2O, CO2) in the Martian atmosphere is an important part of the puzzle that is water and life on ancient Mars.

Pressure sensor instrument
The Finnish Meteorological Institute developed the pressure sensor instrument for the Phoenix Lander. The pressure sensor is based on Vaisala technology and components. It has three BAROCAP® pressure sensors, and a THERMOCAP® temperature sensor for internal temperature monitoring. The instrument is built around the Vaisala proprietary ASIC (Application Specific Integrated Circuit).

The Phoenix Lander’s pressure sensor is already the fifth Vaisala BAROCAP® pressure sensor to be used on planetary space missions. Three earlier attempts to get the pressure sensor on Mars failed because of unsuccessful spacecraft launches or landings (Mars-96, Mars Polar Lander -99, Beagle-2 -03). The Huygens Lander made a successful landing onto Saturn’s moon, Titan, in 2005, and the onboard BAROCAP® recorded the pressure profile of Titan’s atmosphere during the three hour landing.

Author: Jouni Polkko, Finnish Meteorological Institute, Finland

Further information:
http://phoenix.lpl.arizona.edu/
www.vaisala.com/barometricpressure