Curiosity inside Gale Crater photographed on August 12 by the Mars Reconnaissance Orbiter. The grayish-blue patches near the rover are the blast pattern from the sky crane descent stage. Click image for a monster version. Credit: NASA/JPL-Caltech/University of Arizona
If not kin, Earth and Mars are blood brothers. Both have ice, clouds, storms, volcanoes and desert landscapes to name a few traits in common. We also share similar tilts in our axes and days that are almost identical in length.
Notice I said ‘almost’. The Martian day is 24 hours, 39 minutes and 35 seconds long or 2.7% longer than Earth’s. To distinguish it from an Earth day, scientists call it a “sol”, the Latin word for sun. In previous Mars missions as well as this one, you need to know what time it is at your lander or rover site so you can take pictures and measurements in the light of day and beam them up to the Mars orbiters for relay back to Earth.
Artist’s concept shows the Curiosity using it ChemCam instrument to investigate the composition of a rock surface. ChemCam fires invisible laser pulses at a target. The instrument then views the resulting spark with a telescope and spectrometers to identify the chemical elements. Credit: NASA/JPL illustration
To keep track of day and night at both operating rover sites (Opportunity Rover is still in good health) the teams operating the probes must synchronize their work schedules with Mars time. They do this by using a 24-hour Mars clock where the seconds, minutes and hours are all 2.7% longer than the standard 24-hour Earth clock.
That’s right. Those 40 minutes of extra time in the Martian day are divvied up evenly across the day to create a convenient 24-hour clock where every second is ever so slightly longer than an Earth second.
Planning life around Martian sunrise and sunset for the Earth-bound comes with interesting and sometimes painful consequences. Mission controllers’ work schedules slip out of synch with Earth time by 40 minutes a day. Many of us start work at the same time every day of the week. Rover operators begin their shift 40 minutes later each day. Huh?
NASA/JPL ground controllers celebrate when they see the first images transmitted back from Curiosity after a successful landing on Mars August 5-6, 2012. They’ll soon be living on Martian time. Credit: NASA – Bill Ingalls
Let’s say Curiosity’s operator and I both start work on Monday at 10 a.m. Remember, he’s using a watch synchronized to Mars time and I’ve got a cheap Earth watch from Target.
The next day we both start work again at 10 a.m. according to our watches. Can you guess what happens? He shows up 40 Earth minutes late even though his watch reads 10 a.m. just like mine. By the end of the week, the rover driver starts work 4 x 40 minutes or more than 2 1/2 hours late. After 18 days, he’s coming to work at 9 p.m. Earth time and working a long, lonely night! Yet his watch still tells him he’s arriving to work on time at 10 a.m. Again, this is because Mars’ day is 40 minutes longer than Earth’s.
You can imagine how a Mars work schedule must wreak havoc with your personal life. A day shift soon morphs into an evening shift and then an overnight. One entire cycle – the number of days it takes to get back in synch with Earth time – takes 36.5 days or a little more than five weeks. These men and women are working days and night over that time. Getting a good night’s rest must have been challenging.
Garo Anserlian, master watch and clockmaker, devised the first watch to tell Mars time. A Mars day, called a sol, is divided into 24 hours like an Earth day but 40 minutes longer. Credit: NASA
So it was for scientists involved with the previous two Mars rovers, Opportunity and Spirit. To help keep everything on schedule without having to constantly translate from Earth time to Mars time, system engineers involved with those missions went on a hunt to find a watchmaker to build a Mars watch. Enter Garo Anserlian of Executive Jewelers in the little town of Montrose, California.
He took up the challenge, attaching tiny weights to clock innards, to lengthen an ordinary Earth second into a Martian one. Members of the rover team each got a custom watch geared to Mars time to help them plan daily rover activities. That was back in 2003-2004. Now Anserlian sells Mars watches to regular folks at $295 a pop. Check out his site if you’re interested.
A Mars watch for sale by Anserlian’s Executive Jewelers store. Credit: Executive Jewelers
While today is only Sol 10 for Curiosity, the 10th Mars day since the landing, it’s Sol 3,044 for the Opportunity rover which landed in January 2004. I wondered whether the Opportunity Rover folks were still bound to Mars time after more than 8 years of the rover’s operation on the planet. To find out I called D.C. Agle in the Jet Propulsion Lab’s (JPL) newsroom.
For the first 90 days of the mission, they lived like Martians but since then JPL’s worked out a “more livable” arrangement. With Curiosity, the team of scientists and engineers will also clock their days by the punishing Mars schedule for the coming 3 months.
Some of the scientists still wear the watches, but most are now using desktop Mars clocks or Smartphone apps. Agle uses the free NASA program called Mars 24 for PC or Mac. It’s a Java application that displays Martian times for both Curiosity and Opportunity Rovers and a representation of the planet showing its current sun- and night sides. Get it HERE and feel (almost) like you’re living on Mars. There’s currently no NASA Smartphone app for Mars time, but several others are available at online stores:
* Mars Clock and Mars Surface Times for iPhone, iPad and iPod Touch
* Martian Time for Android
A screen grab from NASA’s free Mars 24 program. You can now have you own Mars clock right on your computer desktop. Credit: NASA GISS
One last time tidbit. Many of us watched the final minutes of Curiosity’s thrilling descent to Mars last earlier this month. While it all seemed to be happening moment-by-tense-moment, the probe had already landed 14 minutes earlier. Done deal. It took radio communications traveling at the speed of light 14 minutes to make the trip back to Earth. To quote the late Johnny Carson: “That is wild stuff.”