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Gazing Down on the Moon, Touching Down on Mars

by Geoff Chester, USNO Public Affairs | 16 February 2021

by Geoff Chester, USNO Public Affairs | 16 February 2021

Location of Jezero Crater on Mars, based on map made during opposition October-November 2020
with a Celestron 23.5-cm (9.25-inch) f/10 Schmidt-Cassegrain telescope, 2.5X TeleVue Barlow lens,
and a ZWO ASI224MC color imager.

The Moon waxes in the evening sky this week, reaching her First Quarter phase on the 19th at 1:47 pm Eastern Standard Time.  During the week Luna climbs rapidly northward along the ecliptic, placing her in ideal observing conditions for Northern Hemisphere residents.  On the evening of the 18th she may be found a few degrees south of ruddy Mars.  On the following night you will find her placed evenly between the bright star Aldebaran and the Pleiades star cluster in the constellation of Taurus, the Bull.  The Moon ends the week close to Castor and Pollux, the Twin Stars of Gemini.

While the Moon may appear to be close to Mars on the 18th, that day will also see the arrival of the latest emissary from Earth.  Last week a pair of space probes slipped into orbit around the red planet.  The Hope orbiter, sponsored by the United Arab Emirates, arrived on the 9th, while the next day the ambitious Chinese Tianwen-1 mission settled into orbit as well.  On the 18th the American Perseverance roving vehicle will arrive for a direct entry and landing on the martian surface.  Perseverance is the successor to the Curiosity rover, which touched down on Mars on August 5th, 2012 and is still going strong.  Like Curiosity, Perseverance is powered by a nuclear generator and is about the size of a small SUV.  It carries a battery of cameras and other instruments to analyze the soil of its target site, Jezero crater, which is believed to be an ancient lake bed that formed early in Mars’ geological past.  Perseverance will also collect samples of rocks and soil that will be left for a future lander to pick up and return to Earth.  In addition to these ambitious goals, the rover will also deploy the first flying drone on Mars, a small solar-powered helicopter dubbed “Ingenuity”.  The landing will take place at around 3:00 pm EST.  “Live” coverage will be streamed on NASA TV, but you won’t actually see events occur in real time.  Due to the distance between Earth and Mars communications from Perseverance will take over 11 minutes to travel to us at the speed of light.  The mission will either succeed or fail four minutes before we endure the “seven minutes of terror” that make up the entry, descent, and landing phases of the flight.

As we reach out to virtually “touch” the surface of Mars, you can use this week to explore the varied surface features of our own natural satellite, the Moon.  The evenings before and after First Quarter are my favorite times to bring the Moon closer via my telescopes.  The stark beauty of the Moon can be appreciated with just about any optical aid, but I am partial to smaller instruments which tend to be less affected by the unsteadiness of our atmosphere.  A good four-inch aperture telescope will reveal an astonishing array of features from night to night as the terminator line slowly creeps across Luna’s face.  It is often said that the Moon is “looked over, then overlooked” by novice amateur astronomers, but she is well worth spending the time to give her close scrutiny.  While her major features have been frozen in time for hundreds of millions of years, it is still possible to see something new at each lunation as the play of sunlight and shadow highlight old familiar features in new ways.  That’s why I have come back to look at her each month for decades.

As we’ve mentioned, Mars is undergoing an invasion of sorts from the denizens of Earth.  The red planet has piqued our curiosity for centuries ever since the first crude sketches of surface features were secured by the astronomer Christiaan Huygens in 1659.  The planet comes to opposition every 2.14 years on average, presenting us with our best chances to observe his dusty surface from Earth.  His most recent opposition in October 2020 saw him briefly shine as the brightest planet in the sky after Venus.  He has now faded as Earth leaves him behind and is now prominent only because he is located in a sparsely populated part of the sky. 


Commander, Naval Meteorology and Oceanography Command | 1100 Balch Blvd. | Stennis Space Center, Mississippi 39529

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