A Workday on Mars is More Than 9-to-5:40
For Phoenix Mars Lander Scientist John Hoffman, a Year Lasts 687 Days
July 18, 2008
The average day, or “sol,” on Mars is 40 minutes longer than our 24-hour day on Earth. UT Dallas Physics Professor John Hoffman has spent more than 50 days on Martian time analyzing soil from the surface of the Red Planet.
A day in the life
• Days begin on Martian time roughly 40 minutes later each day due to the length of the Martian day, or “sol.”
• The research team holds a brief kickoff meeting about 30 minutes before the first satellite data comes back from Mars.
• The team spends a couple hours reviewing the day’s first batch of data.
• Team members sit down again for a mid-point meeting and get a report on the condition of the lander’s instruments.
• The sol ends, and the team holds another meeting to look at the day’s data and plan the next day.
• A new block of commands, the lander’s “to do list,” is beamed up for the next day.
Hoffman, a member of the UT Dallas William B. Hanson Center for Space Sciences, designed a mass spectrometer system that analyzes gases from soil samples heated in eight small furnaces aboard the Phoenix Mars Lander.
The spectrometer’s job is to tell scientists the makeup of the planet’s soil, including water, minerals and metals.
“We can only communicate with the Lander at certain times,” Hoffman said. “We use two satellites, the Mars Odyssey and the Mars Reconnaissance Orbiter. When the mission started on May 25th, it took about 15 minutes to transmit a signal between the lander and the Spacecraft Operations Center (SOC). Now it’s up to almost 20 minutes one-way for the signal, which travels at the speed of light.”
An enormous amount of planning and coordination takes place at the SOC, which is owned and operated by the University of Arizona in Tucson. Hoffman and the research team, led by Dr. Peter Smith of the University of Arizona, send commands to the lander at the end of each workday. Batches of programs, called blocks, comprise the lander’s “to do list” for the next sol.
Hoffman said the lander’s solar power system is working better than expected, so scientists are getting 12-hour work days from a lander that was supposed to work only six-hour stretches. It’s one way to expand the mission, which was slated to last for only 90 sols. The lander has proved so efficient that Hoffman said it could go beyond that—into what NASA calls an “extended mission.”
Part of what determines whether a mission can be extended is how intensive and expensive maintenance can be for a lander many thousands of miles from home and sitting atop a fairly harsh environmental platform.
“The nights on Mars drop down to 80 or 90 degrees below 0 C on Mars,” Hoffman said. “We wake up the lander by warming its electronics up, sort of like a boost of coffee in the morning. Once the instruments are warmed up, we can start doing some science.”
In some ways, Mars has been stubborn to give up its secrets. Though tantalizing imagery and data from the Red Planet shows suspected ice and water flows, Hoffman’s spectrometer must analyze samples baked at 1,800 F (1,000 C) to definitively show evidence of anything specific. A 7-foot-long robotic arm on the unmanned lander scoops soil samples into any of eight, one-time-use ovens. Only a couple of the ovens have been used so far, so plenty remain available to answer questions about the make-up of the Martian soil.
“We’ve had our challenges,” Hoffman said. “We scooped some soil and dropped it on a screen above one of the ovens. We sift the soil, just like sifting flour for baking, to make sure we don’t get large bits of rocks inside the ovens. The first sample didn’t want to sift through the screens. We sifted and shook the sample in six different sols until it finally dropped in the oven where we could heat it and take a look at the results.”
Hoffman is upbeat about the data coming back from lander’s work each day. After calibration runs and sorting through some electronic challenges (a short halted work briefly until the extent and cause could be studied), the research team is again gathering data and pouring over the results.
“The areas we’re looking at are named after Disney characters,” Hoffman said. “One feature on the soil was Baby Bear,” which, Hoffman said with a grin, “we put in the oven. Mama Bear and Papa Bear are other areas of interest, as is Goldilocks. Right now we’re looking at samples in an area the lander dug called Snow White trench. There’s a very hard layer there—we think it may be ice. Figuring out how much energy it takes to melt the samples we’ve scooped up will be one of the measurements that definitively confirms the substance is ice. And we’ll also measure water vapor with the mass spectrometer.”
This image from the 49th Martian day of the mission, shows the Phoenix Mars Lander’s Robotic Arm. (Image courtesy of NASA/JPL-Caltech/University of Arizona)
About Dr. John Hoffman
Dr. Hoffman’s instruments have helped unpack the mysteries of our solar system from three Apollo missions to the moon, to the Pioneer Mission to Venus in 1978, to the landmark Phoenix Mission to Mars in 2008.
His spectrometer helped explore Haley’s Comet in 1986, and his experiments still revolve around the earth on a handful of orbiting satellites. The recent Phoenix Mars Mission depends heavily on a system of small furnaces and a mass spectrometer system he designed to determine the presence of water and to study the mineralogical composition of soil on the Red Planet.
Hoffman’s spectrometer will also take a look at the skies above Mars to analyze the planet’s atmosphere. A pioneering space scientist for more than four decades, Hoffman has explored space from his planetary laboratory at UT Dallas and its predecessor institution since 1966.