One of the complications of interplanetary research is that the probes you’ve placed on the other planet can’t be reached via radio while the planet they are on passes to the other side of the sun, which happens now and then. In fact, for the days before and after Mars is opposite the sun, communication is risky because it is remotely possible that something could be misunderstood if the signal is messed up by passing near the sun. So, from January 27th through February 11th there will be no talking to the Rovers on Mars (but some listening).

Conveniently, Opportunity Rover has arrived at a rock that happens to be of interest. The mass spec on Opportunity uses a radioactive source to elicit readings from rocks, but that source is rather old (half life of about a year, and it’s been a few years…) so the mass spec has to stare at a rock for a week or so to make sense of it. So, NASA will have Opportunity staring at this one rock for the entire time. Pity, because it might have been interesting to see if Opportunity could tell us what the other side of the sun looks like….

Read the rest of the story here.


  1. #1 Dave X
    January 21, 2011

    Similar to the dark side of the moon?

  2. #2 LarianLeQuella
    January 21, 2011

    The Martians know all about this! This will be exactly the time they will come out for their party, and to make funny faces at the rover. Lots of laughs for them!


    Actually, what I find funnier (sader?) is that if you mention this to people, it will be an idea or concept that they have never even considered, and sometimes have a hard time comprehending. It’s like people still believe in a geocentric universe…

  3. #3 dean
    January 21, 2011

    “This will be exactly the time they will come out for their party, and to make funny faces at the rover. Lots of laughs for them!”

    Then they will fart in its general direction.

    I see Dave beat my question: I assume that this is the same issue we (at least I, I don’t know how old others here are) heard during lunar missions when we were told the astronauts’ orbiter was passing behind the moon and communication would go away until they came out?

  4. #4 Joshua Zelinsky
    January 21, 2011

    The sun rotates already (equator completes a rotation every 25 days) so we know what the sun looks like from the other side.

  5. #5 Greg Laden
    January 21, 2011

    It is a little different than the dark side of the moon, yet similar. Similar in that its a communication blackout. Different in that the moon’s “other” side (whcih is not all dark except during what we see as a full moon, and is totally lit when we see a “new” moon) is always on the other side … on mars, the planet rotates, and thus the rovers rotate outside of radio contact with earth once every Martian day. However, there are satellites in orbit over Mars that allow continued contact by relay. I’m actually not sure how often there is a blackout with communication given the current setup. I’ll ask.

    (The martian day is essentially the same as the earth day, about 23 hours or so)

    What is happening here is more like an eclipse. Well, it is exactly like an eclipse, but the planet Mars is getting eclipsed by a star.

  6. #6 Greg Laden
    January 21, 2011

    Joshua, yeah, but it’s at night so we can’t see it….

  7. #7 Amy
    January 21, 2011

    I’ll ask.

    Ask who?

  8. #8 Greg Laden
    January 21, 2011

    I asked NASA.

  9. #9 Joshua Zelinsky
    January 21, 2011

    Greg, huh? It is rotating over a period much longer than the Earth day. You get to see all of the sun during daytime over a 40 day period or so.

  10. #10 Greg Laden
    January 21, 2011

    That was a joke. Like, the sun has a sunny side and a night side. Astronomy joke.

  11. #11 Benton Jackson
    January 21, 2011

    This joke:

    A Russian, an American, and a Blonde were talking one day.
    The Russian said, ‘We were the first in space!’
    The American said, ‘We were the first on the moon!’
    The Blonde said, ‘So what? We’re going to be the first on the sun!’ The Russian and the American looked at each other and shook their heads.
    ‘You can’t land on the sun, you idiot! You’ll burn up!’ said the Russian.
    To which the Blonde replied, ‘We’re not stupid, you know. We’re going at night!’

  12. #12 Joffan
    January 21, 2011

    Martian solar day is 24 hours and 39.6 minutes. Kim Stanley Robinson’s Red/Green/Blue Mars trilogy had the extra 40 minutes or so as a kind of daily leap-period.

    This syzygy is ideal as an excuse to keep the word “syzygy” alive.

  13. #13 bcoppola
    January 21, 2011

    On Mars, does Opportunity only stare once?

  14. #14 Virgil Samms
    January 22, 2011

    Rover communications will continue to be monitored from Mirror Earth, exactly opposite us in orbit, where our evil twins all have goatees.

  15. #15 Tony P
    January 22, 2011

    I’m continually impressed that one of the two Mars rovers is still actively exploring the planet, many years after it was supposed to fail.

    Both Opportunity and Spirit are and were testaments to good engineering practice.

  16. #16 Updated
    January 24, 2011

    UPDATE: Answer on the question of when Earth and Rovers are in vs. out of radio contact: