Month: February 2018

2018, February 26: The Morning Planet Parade

The morning planet parade continues as the three bright outer planets — Jupiter, Mars. and Saturn — shine from the southern sky this morning during early twilight.

Jupiter, the brightest of the three planets, shines from the stars of Libra.  It is 7.7 degrees from Zubenelgenubi, the brightest star in the constellation.  Jupiter passes the star again during June as it retrogrades.

Mars appears near its rival — Antares.  Mars passed the star earlier this month.   This morning the two are 10 degrees apart.  Mars is slowly marching eastward, passing Saturn in early April.

Saturn is 18.3 degrees to the lower left of Mars.  It is above the stars of Sagittarius, which are low in the sky at this time.

The articles that follow provide details about the planets visible without optical assistance (binoculars or telescope):

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2018, February 25: Welcome Back, Venus!

Welcome Back Venus. The planet appears low in the sky during bright twilight.

After many days of raining and cloudy weather, the sky cleared this evening to catch a view of Venus during bright evening twilight.  Binoculars were needed to initially find it; it then became visible to the unaided eye as the sky darkened.

Venus began its evening appearance at its superior conjunction on January 9.  It is slowly climbing back into the sky after passing on the far side of the sun during daylight hours.

Next weekend, Venus and Mercury appear about one degree apart.  See the link at in the listing below to get more details of this conjunction.  Another conjunction with these two planets occurs on March 18.

The articles that follow provide details about the planets visible without optical assistance (binoculars or telescope):

2018, February 12: Jupiter, Mars & Saturn

After several days of cloudy, snowy weather, three planets and the moon shine in the early morning sky.

Bright Jupiter is in the south, 7 degrees from the star Zubenelgenubi.  Jupiter passes the star again in June as it retrogrades.

Mars, 17.9 degrees to the lower left of Jupiter, appears above the star Antares (The Rival of Mars).  The star is so named because its brightness and color are similar to the planet.  Mars is 5.1 degrees above Antares this morning.  Mars passed closest to Antares on February 10.

Watch Mars approach and pass Saturn.  They are closest on April 2.

Saturn is low in the southeastern sky, nearly 44 degrees to the lower left of Jupiter.

The waning crescent moon (26.5 days old) appears to the lower left of Saturn, outside of the frame of the image at the top.  New moon is February 15.

The articles that follow provide details about the planets visible without optical assistance (binoculars or telescope):

2018, February 8: NASA News, Tiny Crystal Shapes Get Close Look From Mars Rover

Star-shaped and swallowtail-shaped tiny, dark bumps in fine-layered bright bedrock of a Martian ridge are drawing close inspection by NASA’s Curiosity Mars rover.

This set of shapes looks familiar to geologists who have studied gypsum crystals formed in drying lakes on Earth, but Curiosity’s science team is considering multiple possibilities for the origin of these features on “Vera Rubin Ridge” on Mars.

One uncertainty the rover’s inspection may resolve is the timing of when the crystal-shaped features formed, relative to when layers of sediment accumulated around them. Another is whether the original mineral that crystallized into these shapes remains in them or was subsequently dissolved away and replaced by something else. Answers may point to evidence of a drying lake or to groundwater that flowed through the sediment after it became cemented into rock.
The rover team also is investigating other clues on the same area to learn more about the Red Planet’s history. These include stick-shaped features the size of rice grains, mineral veins with both bright and dark zones, color variations in the bedrock, smoothly horizontal laminations that vary more than tenfold in thickness of individual layers, and more than fourfold variation in the iron content of local rock targets examined by the rover.

“There’s just a treasure trove of interesting targets concentrated in this one area,” said Curiosity Project Scientist Ashwin Vasavada of NASA’s Jet Propulsion Laboratory, Pasadena, California. “Each is a clue, and the more clues, the better. It’s going to be fun figuring out what it all means.”
Vera Rubin Ridge stands out as an erosion-resistant band on the north slope of lower Mount Sharp inside Gale Crater. It was a planned destination for Curiosity even before the rover’s 2012 landing on the crater floor near the mountain. The rover began climbing the ridge about five months ago and has now reached the uphill, southern edge. Some features here might be related to a transition to the next destination area uphill, which is called the “Clay Unit” because of clay minerals detected from orbit.
The team drove the rover to a site called “Jura” in mid-January to examine an area where — even in images from orbit — the bedrock is noticeably pale and gray, compared to the red, hematite-bearing bedrock forming most of Vera Rubin Ridge.

“These tiny ‘V’ shapes really caught our attention, but they were not at all the reason we went to that rock,” said Curiosity science-team member Abigail Fraeman of JPL. “We were looking at the color change from one area to another. We were lucky to see the crystals. They’re so tiny, you don’t see them until you’re right on them.”
The features are about the size of a sesame seed. Some are single elongated crystals. Commonly, two or more coalesce into V-shaped “swallowtails” or more complex “lark’s foot” or star configurations. “These shapes are characteristic of gypsum crystals,” said Sanjeev Gupta, a Curiosity science-team member at Imperial College, London, who has studied such crystals in rocks of Scotland. Gypsum is a form of calcium sulfate. “These can form when salts become concentrated in water, such as in an evaporating lake.”
The finely laminated bedrock at Jura is thought to result from lakebed sedimentation, as has been true in several lower, older geological layers Curiosity has examined. However, an alternative to the crystals forming in an evaporating lake is that they formed much later from salty fluids moving through the rock. That is also a type of evidence Curiosity has documented in multiple geological layers, where subsurface fluids deposited features such as mineral veins.

Some rock targets examined in the Jura area have two-toned mineral veins that formed after the lake sediments had hardened into rock. Brighter portions contain calcium sulfate; darker portions contain more iron. Some of the features shaped like gypsum crystals appear darker than gypsum, are enriched in iron, or are empty. These are clues that the original crystallizing material may have been replaced or removed by later effects of underground water.

The small, stick-shaped features were first seen two days before Curiosity reached Jura. All raw images from Mars rovers are quickly posted online, and some showing the “sticks” drew news-media attention comparing them to fossils. Among the alternative possibilities is that they are bits of the dark vein material. Rover science team members have been more excited about the swallowtails than the sticks.

“So far on this mission, most of the evidence we’ve seen about ancient lakes in Gale Crater has been for relatively fresh, non-salty water,” Vasavada said. “If we start seeing lakes becoming saltier with time, that would help us understand how the environment changed in Gale Crater, and it’s consistent with an overall pattern that water on Mars became more scarce over time.”
Such a change could be like the difference between freshwater mountain lakes, resupplied often with snowmelt that keeps salts diluted, and salty lakes in deserts, where water evaporates faster than it is replaced.

If the crystals formed inside hardened rock much later, rather than in an evaporating lake, they offer evidence about the chemistry of a wet underground environment.
“In either scenario, these crystals are a new type of evidence that builds the story of persistent water and a long-lived habitable environment on Mars,” Vasavada said.
Variations in iron content in the veins, smaller features and surrounding bedrock might provide clues about conditions favorable for microbial life. Iron oxides vary in their solubility in water, with more-oxidized types generally less likely to be dissolved and transported. An environment with a range of oxidation states can provide a battery-like energy gradient exploitable by some types of microbes.

“In upper Vera Rubin Ridge, we see clues that there were fluids carrying iron and, through some mechanism, the iron precipitated out,” Fraeman said. “There was a change in fluid chemistry that could be significant for habitability.”

Source

2018, February 5: Jupiter, Mars and Saturn

The three bright outer planets shine in a clear, cold sky this morning,  Bright morning star Jupiter is in the southern skies.  It is 6.8 degrees from Zubenelgenubi.  Jupiter slowly moves eastward compared to the starry background until March 8 when it begins to retrograde.  It passes Zubenelgenubi in June as it retrogrades.

To the lower left of Jupiter, Mars continues its eastward march.  It is 14.8 degrees from Jupiter.  Mars passes 5 degrees from Antares on February 10.

Meanwhile, Saturn is emerging from the sun’s bright glare of its solar conjunction.  It is 29 degrees to the lower left of Mars.  Mars passes Saturn on April 10.  Watch Mars continue to move away from Jupiter, past Antares, and toward Saturn each clear morning.

The articles that follow provide details about the planets visible without optical assistance (binoculars or telescope):

2018, February 2: Jupiter, Mars and Saturn

Bright Jupiter, Mars and Saturn shine during morning twilight today.

Jupiter is 6.1 degrees from Zubenelgenubi, the Southern Claw.  The planet is slowly moving eastward compared to the background stars.  It begins retrograding on March 8, passing Zubenelgenubi again in early June.

Mars is dimmer and marching to the east.  This morning it is 7.7 degrees from Antares.  Mars passes Antares on the morning of February 10.

Saturn is farther east and lower in the sky.  It is nearly 31 degrees from Mars.  Mars passes close to Saturn on April 2.  Watch Mars close in.

The articles that follow provide details about the planets visible without optical assistance (binoculars or telescope):