Martian Sunrise
Published on Aug 30, 2008 at 10:17 am.
2 Comments.
Filed under Mars.
The Phoenix Lander is so far north on Mars that it is a little north of the Martian Arctic Circle. That means that in the peak of the summer, the Sun doesn’t set there. Conversely, it also means that the Sun doesn’t rise in the dead of winter. For a spacecraft that is solar powered, perpetual sunlight is a good thing. Of course, the reverse is true: perpetual night is a bad thing. The Phoenix landed during the Martian northern hemisphere’s summer. So, it was able to take advantage of perpetual sunlight for nearly three months. But, that is now over. On its 86th day on Mars, the Sun set. It might not have set then if the horizon had been perfectly flat, though. Rather, there was a shallow hill to the north, and the Sun went behind that for a while. It didn’t stay down long, though. The night only lasted about half an hour. As on Earth, though, this first sunset north of the Arctic Circle resulted in a period of twilight rather than true darkness. But, the nights will quickly be getting longer, and soon there will be actual dark nights, not twilight. Each day, the Sun makes an arc in the sky of increasing radius as Mars’ north pole swings away from the Sun due to the planet’s motion along its orbit. So, the Sun will dip farther and farther below the horizon, and the location along the horizon where it rises and sets will gradually move southward. Eventually, the Sun will rise almost where it sets towards the South. Then, it will not rise again for a very long time. The Phoenix, though, will be long dead by then.
The image here was taken a few days ago on the morning of the lander’s 90th day on Mars (Sol 90). The Sun set on Sol 89, and rose again about 75 minutes later. Phoenix is solar powered, but it has batteries that carry in through the night. But, the Sun is very low in the sky, so it does not provide a lot of power to the solar panels to keep the batteries charged. Of course, its designers knew that before sending the spacecraft there, so the solar panels are quite large compared with other craft that we’ve sent to Mars. But, the lower the Sun gets, the harder it will be for the solar panels to keep the batteries charged. It will also be getting colder at night, requiring an increased load on the batteries to keep the lander warm enough to continue operations. Eventually, the batteries will not be able to keep up with the demand, and they will drain to the point that they die. Phoenix will then expire. NASA says that they’ll try sending a signal to the lander once the Martian winter is over, but there is almost no hope that the spacecraft will be able to respond. During the dead of winter, it will get so cold that carbon dioxide, the primary constituent of the Martian atmosphere, will freeze. Phoenix will be buried under a sheet of dry ice. Even the most optimistic scientist and engineer would be surprised for it to be able to regain function after the long Martian winter (almost twice as long as an Earth winter).
However, in the mean time, Phoenix does continue to operate quite well and is still making discoveries and is still sending back useful data. It is already past its expected mission lifetime and is into an extended mission phase. The spacecraft is healthy enough to continue its work for some time to come.
-Astroprof
Image courtesy NASA, UA
Sili on August 30, 2008 at 12:29 pm: 1
I’m glad to hear that they are at least going to check.
Not that I’ll have my hopes up, but just look at the rovers. And they’ve shown what they can do with Hirise, and they know where to look for Phoenix (unlike the failed missions).
Here’s hoping they get to use all the ovens and beakers before it’s too late.
Astroprof’s Page » Sun setting on Phoenix on October 29, 2008 at 7:19 pm: 2
[…] of 68° 13′ N, the Sun does not set near the summer solstice. But, earlier this year, Phoenix got to experience sunrises and sunsets. While that might be interesting to us humans, it is a problem for a solar […]