Table of Contents

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.”


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):

2018, January 31: Mount Sharp ‘Photobombs’ Mars Curiosity Rover

This self-portrait of NASA’s Curiosity Mars rover shows the vehicle on Vera Rubin Ridge, which it’s been investigating for the past several months. Poking up just behind Curiosity’s mast is Mount Sharp, photobombing the robot’s selfie. Image credit: NASA/JPL-Caltech/MSSS

A new self-portrait of NASA’s Curiosity Mars rover shows the vehicle on Vera Rubin Ridge, which it has been investigating for the past several months. Directly behind the rover is the start of a clay-rich slope scientists are eager to begin exploring. In coming weeks, Curiosity will begin to climb this slope. In the image, north is on the left and west is on the right, with Gale Crater’s rim on the horizon of both edges.

Poking up just behind Curiosity’s mast is Mount Sharp, photobombing the robot’s selfie. When Curiosity landed on Mars five years ago, the team’s intention was to study lower Mount Sharp, where the rover will remain for all of its time on Mars. The mountain’s base provides access to layers formed over millions of years. These layers formed in the presence of water — likely due to a lake or lakes where sediments accumulated, which formed these layers inside Gale Crater.

The mosaic was assembled from dozens of images taken by Curiosity’s Mars Hands Lens Imager (MAHLI). They were all taken on Jan. 23, 2018, during Sol 1943.


2018, March 3: Venus – Mercury Conjunction

Update: Mercury passes about 1 degree from Venus on March 3.

Brilliant Evening Star Venus and bright Mercury shine during the evening twilight on the evening of March 3.  Both planets are emerging from their superior conjunctions.  Mercury’s conjunction is February 17; Venus was January 9.

The chart above shows the planets about 30 minutes after sunset.  Brilliant Venus is 5 degrees above the horizon.  Mercury is 1 degree to the right.  It is bright, yet about 5 times dimmer than Mercury.  Binoculars may be required to first identify Mercury.  It should easily viewed without optical assistance once it’s located.

Find a clear western horizon to locate the pair.


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

2018, January 30: NASA NEWS – Vista From Mars Rover Looks Back Over Journey So Far

A panoramic image that NASA’s Curiosity Mars rover took from a mountainside ridge provides a sweeping vista of key sites visited since the rover’s 2012 landing, and the towering surroundings. (Click the images to read the detailed captions.)

The view from “Vera Rubin Ridge” on the north flank of Mount Sharp encompasses much of the 11-mile (18-kilometer) route the rover has driven from its 2012 landing site, all inside Gale Crater. One hill on the northern horizon is about 50 miles (about 85 kilometers) away, well outside of the crater, though most of the scene’s horizon is the crater’s northern rim, roughly one-third that distance away and 1.2 miles (2 kilometers) above the rover.

Curiosity Project Scientist Ashwin Vasavada gives a descriptive tour of the Mars rover’s view in Gale Crater. The white-balanced scene looks back over the journey so far.

Curiosity’s Mast Camera, or Mastcam, took the component images of the panorama three months ago while the rover paused on the northern edge of Vera Rubin Ridge. The mission has subsequently approached the southern edge of the ridge and examined several outcrop locations along the way.

Last week, the Curiosity team on Earth received copious new images from the rover through a record-setting relay by NASA’s MAVEN orbiter — surpassing a gigabit of data during a single relay session from Mars for the first time in history.

The team is preparing to resume use of Curiosity’s drill for acquiring powdered rock samples to be analyzed by laboratory instruments inside the rover, more than a year after the most recent of the 15 times the drill has pulled sample material from Martian rocks.

Inside an Impact Crater

Mount Sharp stands in the middle of Gale Crater, which is 96 miles (154 kilometers) in diameter.

“Even though Curiosity has been steadily climbing for five years, this is the first time we could look back and see the whole mission laid out below us,” said Curiosity Project Scientist Ashwin Vasavada of NASA’s Jet Propulsion Laboratory, Pasadena, California. “From our perch on Vera Rubin Ridge, the vast plains of the crater floor stretch out to the spectacular mountain range that forms the northern rim of Gale Crater.” The rover photographed the scene shortly before northern Mars’ winter solstice, a season of clear skies, gaining a sharp view of distant details.

Curiosity’s exact landing spot on the floor of the crater lies out of sight behind a slight rise, but the scene includes “Yellowknife Bay.” That’s where, in 2013, the mission found evidence of an ancient freshwater-lake environment that offered all of the basic chemical ingredients for microbial life. Farther north are the channel and fan of Peace Vallis, relics of the streams that carried water and sediment into the crater about three billion years ago.

Sites such as “Kimberley” and “Murray Buttes” along the rover’s route are marked on an annotated posting of the panorama. The Mastcam recorded both a wider version of the scene (from southwest to northeast) with its left-eye, 34-millimeter-lens camera and a more detailed, narrower version with its right-eye, 100-millimeter-lens camera.

The site from which these images were taken sits 1,073 feet (327 meters) in elevation above Curiosity’s landing site. Since leaving that site, the rover has climbed another 85 feet (26 meters) in elevation. In recent days, the Mastcam has recorded component images for a panorama looking uphill southward toward the mission’s next major destination area. That is called the “Clay Unit” because observations from orbit detected clay minerals there.

Record Relay

The opportunity for some high-volume relay sessions with the MAVEN orbiter is helping the Curiosity team gain a bounty of images and other data this month.

Most data from Curiosity, through the years, have been relayed to Earth by NASA’s Mars Reconnaissance Orbiter (MRO) and Mars Odyssey orbiter, which fly in nearly circular, nearly polar orbits predictably passing over Curiosity at about the same times every day. MAVEN, for Mars Atmosphere and Volatile Evolution, flies an elliptical orbit varying more than 40-fold from its nearest to farthest point from Mars. This suits MAVEN’s science focus on Mars’ atmosphere but results in variable coverage for relaying rover data. Usually, MAVEN passes over rover locations when the distance is too large for optimal relays. However, during occasional periods when the low point of its orbit is near Curiosity’s location on Mars, the relays can serve exceedingly well.

“MAVEN definitely has the potential to move lots of data for us, and we expect to make even more use of it in the future,” said JPL’s Roy Gladden, manager of NASA’s Mars Relay Network Office. The Jan. 22 relay of 1,006 megabits topped the previous record of 840 megabits, also set by MAVEN, but might in turn be bested by other favorable MAVEN relay opportunities in coming days.

The rover team intends to put Curiosity’s drill to work on Vera Rubin Ridge before proceding to the Clay Unit. Resuming use of the drill requires an enterprising workaround for a mechanical problem that appeared in late 2016 and suspended use of the drill. A motor within the drill that advances the bit relative to stabilizer points no longer operates reliably.The workaround being evaluated thoroughly on a test rover at JPL does not use the stabilizer points. It moves the whole drill forward, with bit extended, by motion of the robotic arm.

Source: NASA/JPL