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Headshot of Emily Lakdawalla


Posted by Emily Lakdawalla

01-05-2015 18:55 CDT

Topics: Mercury, mission status, MESSENGER

There is one less robot exploring the solar system today. MESSENGER, which has orbited Mercury for four years, finally ran out of fuel and crashed into the planet at 17:26 UT on Thursday, April 30, 2015. The impact happened out of sight of Earth, with MESSENGER occulted by Mercury; we knew it was gone when it failed to reestablish contact with the Deep Space Network a few minutes later.

MESSENGER was just a robot, an inanimate object; but its human operators and fans were full of emotion yesterday as we stood vigil over its final moments. I watched, as I do, on Twitter. Some people responded to the emotional moment with jokes:

Others were sad.

Mary Kerrigan, noting that MESSENGER was crashing near the Mercury crater named for Shakespeare, looked for inspiration from the Bard.

Many, many people just watched, no doubt feeling lots of different things.

MESSENGER was doing science to the very end....

...and even doing science that would never be returned to Earth.

And then it was over. The Deep Space Network antenna at Goldstone listened for MESSENGER to re-emerge from behind Mercury, and it didn't.

But it wasn't completely over. The Deep Space Network station at Canberra kept listening for MESSENGER, just in case. The tracking pass had been scheduled before the final date of MESSENGER's demise was known, and they kept the scheduled pass because of their usual thoroughness.

DSS45 listening for MESSENGER

Glen Nagle

DSS45 listening for MESSENGER
DSS-45 is a 34-meter antenna that was built in 1986 for the Voyager 2 flyby of Uranus. In this photo, taken on the morning of May 1, 2015 (local time), it is listening for a signal from MESSENGER, which had crashed into Mercury the day before.

At first, I found myself at a loss for what to say or think. I had a momentary feeling that the whole mission had never happened. If a spacecraft crashes on a distant planet and there's no human there to hear it, does it make a sound? I had imagined it there at Mercury for so long, and then it didn't exist anymore; I had the disconcerting feeling that I'd imagined it right out of existence. But Sarah Hörst brought me back to Earth with this crucial point:

Indeed, there are lots of space robot people who still have work to do with all the data that MESSENGER returned, down to the last moment.

Shortly after issuing the press release summarizing the spacecraft's death, the MESSENGER mission -- which will continue on Earth, at least, for at least a year or so, as they archive data -- gave us MESSENGER's final image.

And of course there will be another Mercury mission that will allow us puny humans to take the science further, building on what MESSENGER sent us, and Mariner 10 before it.

Farewell, MESSENGER. You did good.

Mercury and the Pleiades, April 30, 2015

Stuart Atkinson

Mercury and the Pleiades, April 30, 2015
A look toward the innermost planet, on the day that its first orbiter crashed to ground.
See other posts from May 2015


Or read more blog entries about: Mercury, mission status, MESSENGER


Jose: 05/01/2015 07:41 CDT

I am sad the mission is over, however, as a long time Planetary Society member, I am happy since I had the opportunity to name one of its craters: "Rivera Crater". My proposal to honor Diego Rivera was selected this week.

Rick: 05/02/2015 03:45 CDT

Well, what can I say, MESSENGER? You were good to the very last drop -- and then some, quite literally! Rest In Peace. R.I.P. MESSENGER.

Anonymous: 05/03/2015 07:58 CDT

Decaying orbits were popular dramatic props in Star Trek. Residual atmospheric drag does bring Earth satellites down over several years, but Mercury has no atmosphere to speak of. Q: What set of influences brought Messenger low?

Rick: 05/07/2015 03:01 CDT

Well. Without fuel (first, the onboard hydrazine was spent; and then the helium used to stabilize it), MESSENGER's orbit was decaying (i.e., gradually spiraling in towards Mercury's surface, for lack of any fuel whatsoever to slow it down, or raise the orbit any longer). Impact was only a matter of time; at least the scientists were at least able to postpone it till the end of the month (4/30/2015), as well as to calculate the impact's exact time. And, who knows? ESA's BepiColombo mission (in 2024?) just might be treated to finding a new crater in Mercury's mid-northern terrain (MESSENGER's gravesite -- R.I.P.)!

wyrmhole: 05/08/2015 01:21 CDT

My understanding is that it is the non-uniform gravity of Mercury, and the effect of solar wind and radiation pressure, that made MESSENGER's orbit unstable.

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