( CNN ) Let 's start with a pop quiz ( space junkies can skip this test ) . True or False , Mercury is : . 1 ) The planet closest to the sun in our solar system . 2 ) So hot that water could n't possibly exist there . 3 ) Something used in old-style glass thermometers . 4 ) A planet you do n't think about very often . Answers : True , False , True ( but not what we 're talking about in this story ) and I 'm guessing No . 4 is true too . If you flunked the test , it might be because Mercury ( the planet ) suffers from bad ( or very little ) press . Or , maybe it 's just bad lighting . Mercury orbits about 35,983,125 miles from the sun . Compare that to Earth -- we 're about 93 million miles from the sun . Mercury 's closeness to the sun makes it hard to see except at dawn and twilight . This may be one reason we do n't think about it much . Venus , on the other hand , the planet between Earth and Mercury , appears to be the brightest planet in the sky . It 's so bright it 's been mistaken for an airplane . Pilot sends plane into dive after mistaking Venus for oncoming plane . But back to Mercury . It 's getting some attention from the media now because it 's about to get a visitor . The NASA spacecraft MESSENGER ( an acronym for MErcury Surface , Space ENvironment , GEochemistry , and Ranging ) is about to crash onto Mercury . The probe was launched in 2004 and traveled more than six and a half years before it started orbiting Mercury on March 18 , 2011 . Now , MESSENGER is running out of fuel and NASA says it will hit the planet 's surface at 8,750 mph ( 3.91 kilometers per second ) around April 30 . You wo n't be able to see it hit because Messenger will crash on the side of Mercury facing away from Earth . There 's no way to save the spacecraft , but mission operators at the Johns Hopkins University Applied Physics Laboratory ( APL ) in Laurel , Maryland , have been doing what they can to delay the inevitable . They 've been using the little bit of fuel left on board to maneuver the spacecraft to keep it in orbit . They 'll do one final maneuver on Friday , April 24 . `` Following this last maneuver , we will finally declare the spacecraft out of propellant , as this maneuver will deplete nearly all of our remaining helium gas , '' mission systems engineer Daniel O'Shaughnessy said at a recent media briefing . `` At that point , the spacecraft will no longer be capable of fighting the downward push of the sun 's gravity . '' But rather than mourn the loss , scientists held a briefing to celebrate the mission 's success . `` For the first time in history we now have real knowledge about the planet Mercury that shows it to be a fascinating world as part of our diverse solar system , '' said John Grunsfeld , associate administrator for the Science Mission Directorate at NASA Headquarters in Washington . One of MESSENGER 's big findings : It sent back data indicating that ice in Mercury 's shadowed polar regions , if spread over an area the size of Washington , would be more than two miles thick , NASA said . It also took some amazing photos of the planet . So the MESSENGER mission is ending , but scientists say they 'll be busy for years studying data from the probe . And if you want to see Mercury with your own eyes , you may be in luck if you can find an area with dark skies . It will be visible in the night sky just before dusk until about the end of May . Your favorite astronomy website will have some helpful guides . Here are a few we found : . • Earthsky.org . • Astronomy . • Sky and Telescope . • Stardate .
Spacecraft to crash on Mercury this month . MESSENGER probe has been in orbit since 2011 .