3973 - MARS - has two moons!

 

-   3973 -   MARS  -  has two moons!     Mars's two moons, Phobos and Deimos, have puzzled researchers since their discovery in 1877. They are very small: Phobos's diameter of 22 kilometers is 160 times smaller than that of our moon, and Deimos is even smaller, with a diameter of only 12 kilometers.

----------------------------------  3973  -  MARS  -  has two moons!

-      Our moon is essentially spherical, while the moons of Mars are very irregularly shaped, like potatoes.   Phobos and Deimos look more like asteroids than natural moons.

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-    Maybe  they might in fact be asteroids that were captured in Mars's gravity field.  Captured objects would be expected to follow an eccentric orbit around the planet, and that orbit would be at a random inclination. In contradiction to this hypothesis, the orbits of the Martian moons are almost circular and move in the equatorial plane of Mars.

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-    So, what is the explanation for the current orbits of Phobos and Deimos?

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-   To solvethis problem the idea was to trace the orbits and their changes back into the past,    The orbits of Phobos and Deimos appeared to have crossed in the past.  This means that the moons were very likely in the same place and therefore have the same origin.

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-   The researchers concluded that a larger celestial body was orbiting Mars back then. This original moon was probably hit by another body and disintegrated as a result.  Phobos and Deimos are the remainders of this lost moon.

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-    The researchers had to refine the existing theory describing the interaction between the moons and Mars.  All the celestial bodies exert tidal forces on each other.  These forces lead to a form of energy conversion known as dissipation, the scale of which depends on the bodies' size, their interior composition and not least the distances between them.

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-    Mars is currently being explored by NASA's InSight mission.   Other Mars probes have suggested that Phobos and Deimos are made of very porous material.

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-    At less than 2 grams per cubic centimeter, their density is much lower than the average density of Earth, which is 5.5 grams per cubic centimeter. There are a lot of cavities inside Phobos, which might contain water ice and that's where the tides are causing a lot of energy to dissipate."

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-    Using these findings and their refined theory on the tidal effects, the researchers ran hundreds of computer simulations to track the orbits of the moons backward in time until they reached the intersection the moment Phobos and Deimos were born.

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-    Depending on the simulation, this point in time lies between 1 and 2.7 billion years in the past.  The exact time depends on the physical properties of Phobos and Deimos, that is, how porous they are.

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-    A Japanese probe scheduled for launch in 2025 will explore Phobos and return samples to Earth. The researchers expect that these samples will provide the needed details about the interior of the Martian moons that will enable more precise calculations of their origin.

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-    Calculations show is that the common ancestor of Phobos and Deimos was further away from Mars than Phobos is today. While the smaller Deimos has remained in the vicinity of where it came into being, tidal forces are causing the larger Phobos to approach Mars, and this process is ongoing.

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-    Computer simulations also show the future development of the moons' orbits. It seems Deimos will move away from Mars very slowly, just as our moon is slowly receding from Earth. Phobos, however, will crash into Mars in less than 40 million years or be torn apart by the gravitational forces as it nears Mars.

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                   April 25, 2023            MARS  -  has two moons!                    3973                                                                                                                          

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--------------------- ---  Tuesday, April 25, 2023  ---------------------------

 

 

 

 

         

 

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3972 - BENNU ASTEROID - sample returns September, 2023.

 

-   3972 -  BENNU  ASTEROID  -  sample returns September, 2023.    The OSIRIS-REx mission unleashed an unexpected explosion when it touched down on asteroid Bennu in October 2020 to collect a precious sample to carry home to Earth.

-----------------  3972  - BENNU  ASTEROID  -  sample returns September, 2023.

-    Mission scientists have described the dramatic sample retrieval, which led to surprising discoveries about the asteroid's nature.    The findings might have implications for a possible future deflection mission, should the 1,640-feet-wide Bennu one of the riskiest known near-Earth asteroids ever threaten to impact the planet.

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-    We expected the surface to be pretty rigid, like touching down on a gravel pile  A little bit of dust flying away and a few particles jumping up.  But, the images after the event showed a giant wall of debris flying away from the sample side.

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-     Six months after sample collection, in April 2021, the researchers got another glimpse of the OSIRIS-REx touchdown site. When the spacecraft first arrived at Bennu, that site, called “Nightingale”, sat within a 65-foot-wide impact crater. After touchdown, mission scientists found a brand new 26-foot-wide gaping hole in the surface, with displaced rubble and boulders scattered around the site.

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-    That's a surprisingly large scar; scientists had expected to scoop out a bit about as wide as the sample collector itself, 12 inches. "But, there clearly was no resistance whatsoever. The surface was soft and flowed away like a fluid.

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-    The probe sank as deep as 30 inches, revealing pristine material that, unlike the asteroid's surface, was unaltered by the steady battering of cosmic rays and the solar wind, the streams of high-energy particles from the sun.

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-    From the measurements acquired during this repeat visit, they calculated that the density of the surface material was only about 31 to 44 pounds per cubic foot.   For comparison, "a typical Earth rock" has a density about six times higher, more like 190 pounds per cubic foot per cubic meter.

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-     A second study, based on measurements of forces exerted on the probe during the impact, confirmed those numbers.   The surface boulders are very porous and there is a lot of void space between them.We expected that small, fine grains and dust would stick to the large boulders and fill the void space and act as a glue to provide some strength, which would allow the surface to push back against the spacecraft more. But it's not there.

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-    Bennu's soft, fluffy nature may complicate a possible future deflection attempt, should astronomers determine the rock threatens to hit Earth. At 1,640 feet wide, a strike by Bennu would cause continent-wide disruption on our planet. And even though NASA estimates the chance of collision at 1 in 2,700 between the years 2175 and 2199, Bennu is still one of the most dangerous asteroids currently known.

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-    Moreover, scientists assume that many asteroids sport a similar "rubble pile" structure: essentially conglomerations of rock, gravel and dirt held together by weak gravitational forces. The sampling experiment at Bennu shows that it's almost impossible to predict how such a rubble pile might respond to an impact.

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-   The touchdown did provide the first experience of really pressing something into the surface.   If we ever go and actually try to deflect something like this, we would need to know what the surface is like so that it doesn't just absorb the impact.

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-   The underground material appeared more red compared to the bluish surface of Bennu, which suggests that cosmic rays and other forms of space weather erode the exposed space rocks. The reddish hues hint that organic molecules, like hydrocarbons, may be present inside the asteroid, which greatly interests researchers trying to understand the origins of life on Earth.

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-    The scientists will have to wait until OSIRIS-REx's scheduled delivery in September 2023 to get their hands on the precious material. During the dramatic sampling attempt, the probe collected almost 9 ounces of asteroid dust, which is somewhat less than the teams had hoped for but still four times more than they need to conduct the analysis.

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-   The OSIRIS-REx mission was recently extended and after the spacecraft drops off its cargo at Earth next year, it will head to Apophis, another high-risk asteroid, which it will visit in 2029.

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                   April 24, 2023                 3972                                                                                                                          

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--------------------- ---  Monday, April 24, 2023  ---------------------------

 

 

 

 

         

 

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3971 - LIFE - how will we detect it on exoplanets?

 

-   3971 -   LIFE  -   how will we detect it on exoplanets?    Is there life on Mars?  Been part of science fiction dramas for decades.  But, so far most of humanity’s forays into the Solar System seeking signs of life have returned only ambiguity.

----------------  3971  -  LIFE  -   how will we detect it on exoplanets?

-    NASA’s Viking 1 lander designed its suite of experiments to find any signs of life, or biosignatures, on the Martian surface, returned a mix of positive and negative results that summed to an indeterminate answer.    Scientists found no signs of life, but insufficient evidence to say there were no signs to be found.

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-   Scientists have a new tool that might make sure future astrobiology experiments return clearer answers about what they find, and what they don’t, wherever they look.

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-    A “Laser Desorption Mass Spectrometer”, or LDMS device using a cutting analysis tool first pioneered in the pharmaceutical industry uses a laser to ionize material from the surface ice of Saturn’s moon Enceladus.   The instrument can detect larger organic compounds more advanced than any of the biosignature detecting tools currently aboard NASA missions.

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-   The LDMS device is really a combination of two pieces of equipment. There is the laser system, which zaps samples of material on other worlds.

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-    Using lasers for this purpose is not entirely novel. NASA’s Perseverance rover carries a Laser Induced Breakdown Spectroscopy instrument that can zap rocks from some distance away and looks for patterns in the light based on how different geological elements absorb light or fluoresce.

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-   But the LDMS instrument is a bit different.  It is not looking at light, it is looking at mass.

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-    When you zap a bit of rock or ice with a laser, you move electrons around, giving the particles in the resulting vapor an electric charge. This allows the instrument to pull them inside using charged plates and guide them into the second part of the instrument, an analyzer known as an “orbitrap”.

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-    An orbitrap contains a central electrode that looks a bit like a football.  The charged particles oscillate around the football at speeds commensurate with their mass. Get their mass, and you know their elemental composition.  Scientists can infer what the molecule is based on the speed at which it oscillates back and forth across this electrode.

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-    An orbitrap is not the only instrument that can analyze particle masses to determine molecular makeup, but it is one of the most accurate. Some very different molecules may possess very nearly the same mass, and ,  some instruments cannot tell them apart. But the orbitrap has high enough resolution that you know exactly what the chemical formula is.

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-    The combined laser and orbitrap analyzer should be capable of detecting larger organic molecules than existing instruments such as the “Sample Analysis at Mars”, or SAM tool on NASA’s Curiosity rover. Instruments like the SAM work by heating samples of soil until volatile compounds begin evaporating.

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-   That system works well for organic compounds that easily become gas, such as methane but it can’t detect larger organic compounds like peptides, which are chains of amino acids.

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-    The LDMS instrument can detect peptides, and while finding peptides on another world wouldn’t be a sure sign of alien life, the more complex the organic molecule you find, the less likely it is to have been created through an abiotic process.

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-       NASA was still planning on sending a lander mission to Europa, the Jovian moon which scientists believe hosts a massive liquid water ocean beneath its icy crust. It’s possible there’s some form of life in those depths, and if any of that water made it to the surface of Europa, a lander sporting an LDMS instrument could detect it.

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-    There was a robotic arm that scooped ice from the surface of Europa. It dumped it into their sample handling system and it delivered to us on plates.  Then we hit the sample with our laser and we get the chemical composition.

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-   But by 2017, budget cuts led NASA to put the Europa lander concept on the back burner, and Arevalo’s LDMS instrument is now a tool awaiting a new mission.

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-     Weighing in at only eight kilograms, compared to the 40 kilograms of the SAM instrument on Curiosity, the LDMS instrument could go anywhere, from Mars to Europa, to Saturn’s moon Enceladus, another icy, ocean-hosting moon like Jupiter’s moon Europa. Jut waiting for a rocket ride!

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                   April 23, 2023     LIFE  -   how will we detect it on exoplanets?        3971                                                                                                                         

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--  email feedback, corrections, request for copies or Index of all reviews

---  to:  ------    jamesdetrick@comcast.net  ------  “Jim Detrick”  -----------

--------------------- ---  Sunday, April 23, 2023  ---------------------------

 

 

 

 

         

 

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3970 - TELESCOPES - working together?

 

-   3970 - TELESCOPES  -  working together?     What’s possible when Earth and space-based telescopes work together? The potential benefits of coordinating ground, orbital and in situ based observations of objects can benefit from the type of coordinated output that can only come from a cohesive team.

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-----------------------  3970  -  TELESCOPES  -  working together?

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-  It takes many telescopes working together.   The different wavelengths contained in the electromagnetic spectrum need to be captured for the full width of to truly understand some transient phenomena.

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-     The electromagnetic spectrum is extremely large.  It includes all types of light, such as radio, infrared, x-rays, ultraviolet and visible light.  There is no one single sensor that can collect data in all of those different wavelengths at the same time.

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-     Therefore, scientists have developed a plethora of instruments that are extremely good at collecting data in one specific spectrum, such as radio (ALMA), or mid-range infrared (James Webb).

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-   The down side of this specialization is that those instruments are blind in other spectral ranges.  If a scientific team is only observing in one type of light, there is a chance that they could miss important aspects of a phenomena they are studying that are only visible in a different spectral band.

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-    Much of the planetary science data collected is the result of spacecraft that are sent to a planetary system to perform in situ observations.  However, due to the high cost of developing space-based systems and then launching them into orbit, mission planners for these in situ missions must be very selective about what types of instruments they allow on board their spacecraft.

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-     What this normally means is that they are not able to bring imagers that are capable of covering the entire electromagnetic spectrum.  That is where coordination with ground and near-earth-orbit based telescopes comes in.

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-     There are many telescopes in those locations, such as the Atacama desert or Hawaii’s Mauna Kea, that are extremely large, and can provide very high resolution images in specific spectral bands, such as radio, microwaves, or infrared. 

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-    Infrared is particularly useful as there is a lot of physical data points that can be obtained in a single measurement, such as pressure, temperature, and molecular abundances.

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-    If a mission planner of a planetary exploration spacecraft mission can coordinate observations with these much larger, specialized observatories, they will no longer need to include them on their own spacecraft. 

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-   Another advantage that earth-based observatories have over their in situ counterparts is their ability to image a whole planet at once.  Many orbiter or fly by missions are only capable of measuring part of their subject at a single point in time. 

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-   This results in a loss of contextual understanding, as dynamic phenomena that might be observed in a single place by the in situ spacecraft might not be present over the entire surface of the planet or moon.  Support from earth-based telescopes, whether on the ground or in space, could provide that larger context that the spacecraft itself lacks.

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-    One in situ planetary mission is the Juno spacecraft currently in orbit around Jupiter.  The resulting coordination between the Juno spacecraft and a series of earth-based observatories resulted in over 40 papers that used data from more than one observational source of the Jupiter system during that time.

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-     Mars is of particular interest, as it is the most studied planet outside of Earth, and the only one with active rovers physically on its surface.  Scientists interested in understanding where the methane from Mars’ atmosphere comes from would certainly benefit from a coordinated observational campaign between several of the orbiters around Mars (TGO and MAVEN), and earth-based telescopes such as NASA’s Infrared Telescope Facility in Hawaii.

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-    The orbiters around Mars provide excellent two-dimensional slices of spectral data as they are passing over a specific strip of the planet.  However, observatories closer to Earth can provide data on the entire hemisphere of the planet that is facing them, and add a layer of depth that would allow scientists to piece together a three-dimensional picture that would be impossible using only data from the orbiters.

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-    There are still some limitations to earth-based observations, such as the fact that methane is present in Earth’s atmosphere as well, which could skew the data when looking at Mars. 

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-    To get around this problem, scientists came up with an ingenious method of only observing Mars while it is moving away from (or toward) Earth at more than 13km a second.  This differential speed red- (or blue-) shifts the spectral signature of the Martian methane enough that it can be differentiated from that simply present in Earth’s atmosphere.

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-   Another particularly interesting target of joint observations is Titan, which has been the subject of intense scrutiny in recent years due to its hydrocarbon lakes, and its methane/ethane based hydrological cycle.

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-    The moon is so interesting it is about to receive it’s own in situ visitor in the form of the “Dragonfly mission”.  When Dragonfly lands in 2034 many Earth-based telescopes will turn their eyes toward Titan, as the data collected from the surface can then be coordinated with more remote observations.

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-    Dragonfly will be equipped a mass spectrometer, which allows the detection of molecules which are impossible to see remotely, and reveals the full composition of the atmosphere.  Earth-based observation could in turn provide context for these measurements.

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-    ALMA is a series of radio telescopes, which are particularly good at observing organic compounds and making detailed maps of its observational subjects.  Both capabilities would be particularly helpful in helping the Dragonfly mission, and ALMA’s operators are already very familiar with Titan.

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                   April 22, 2023          TELESCOPES  -  working together?             3970                                                                                                                        

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--------------------- ---  Sunday, April 23, 2023  ---------------------------

 

 

 

 

         

 

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3969 - DWARF PLANET - Haumea

 

-   3969 -    DWARF  PLANET   -  Haumea.     Haumea is a “dwarf planet” that was first spotted by astronomers looking at observations made between 2003 and 2004, earning it the name “2003 EL61”.

------------------------  3969  -  DWARF  PLANET   -  Haumea

-    Until 2008, it was classified as a Kuiper Belt Object (KBO),  a reclassification by the International Astronomical Union deemed it a dwarf planet, joining, Pluto, Eris, and Makemake in the Kuiper Belt and Ceres in the asteroid belt.

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-   Located in the Kuiper Belt beyond Neptune, this frigid dwarf planet reaches both opposition (the point directly opposite the sun from the perspective of Earth) and perigee (the point in its orbit closest to Earth) tonight. It visible in the night sky in the constellation Boötes.

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 -    At that time, it was given the name Haumea after the Hawaiian goddess of fertility.  The dwarf planet, which is roughly the size of Pluto, takes about 285 years to orbit the sun, and its distance from Earth varies from 34 to 51 astronomical units, or AU (one AU is the distance between the Earth and the Sun). As it's reaching perigee, that puts it at a distance of 34 AU.

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-    Haumea spins so fast that its shape is more football-like than round. Though its orbit might be quite slow, Haumea rotates extremely fast.   It takes just four hours to complete one rotation. Because of the centrifugal force it experiences due to this rotational speed, Haumea is stretched out like a football instead of round like most other planets and dwarf planets.

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-     Haumea is also the only known dwarf planet to have rings, and it also has two small moons, Namaka and Hi'iaka, which are the daughters of Haumea in Hawaiian mythology.

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-    Haumea, together with Pluto, Makemake, and Eris, lies in the Kuiper belt. This area is like the bigger asteroid belt, located beyond Neptune’s orbit. The other known planet, Ceres, is located in the main asteroid belt.

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-    The ellipsoid shape of Haumea is believed to be the result of its rapid rotation. Think of the way a water balloon stretches out when thrown with a spin. This rotational speed, along with its collisional origin makes Haumea one of the densest dwarf planets discovered to date.

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-  It has two small satellites (moons) called Hi’iaka & Namaka. These were discovered in 2005 using the W.M. Keck Observatory.

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-    Haumea’s moons are thought to be the result of a collision with a large object billions of years ago. This event caused pieces of Haumea to fragment and begin orbiting the planet.

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-   A ring around Haumea was discovered in 2017. This was the first ring system ever discovered beyond Neptune‘s orbit.

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-    One day on Haumea lasts only 3.9 Earth hours. With that, it is one of the fastest rotating large objects in the solar system.

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-   Haumea is made of rock with a thick coating of ice. It has a high albedo because of crystalline water ice on its surface. In fact, it is believed to be as bright as snow!

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-   According to estimates, Haumea is the third-largest known trans-Neptunian object (TNO). The first two are Pluto and Eris. It has one-third of Pluto’s mass and 1/1400 that of Earth.

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-    Haumea is the third brightest object in the Kuiper belt. That is, after the dwarf planets Pluto and Makemake. On a clear night with a good quality telescope, this makes it possible to see Haumea in the night sky,

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                   April 21, 2023               DWARF  PLANET   -  Haumea             3969                                                                                                                          

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--------------------- ---  Saturday, April 22, 2023  ---------------------------

 

 

 

 

         

 

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3968 - EXOPLANETS - discovering planets around stars?

 

-   3968 -  EXOPLANETS  -  discovering planets around stars?  Scientists have discovered more than 4,000 alien planets since spotting the first ones orbiting a star beyond our sun back in 1992.

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------------  3968  -  EXOPLANETS  -  discovering planets around stars?

-    The exoplanet HIP 99770 b , is seen circling its host star in these images by Japan's Subaru Telescope. Data from Europe’s star-mapping Gaia spacecraft revealed the likely presence of a big exoplanet in this system.  Astronomers have directly detected and imaged a gas giant orbiting another star by combining different techniques for hunting exoplanets.

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-   Star-mapping data combined from the European Space Agency’s (ESA) “Gaia” and older “Hipparcos” missions to identify stars that, based on their apparent movements or wobbles, are likely to be orbited by giant planets.

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-    Observations using the telescope’s coronagraphic adaptive optics and spectrograph instruments in July and September 2020 and May and October 2021 led to the discovery of the exoplanet HIP 99770B.

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-   HIP 99770B is a gas giant planet about 15 times the mass of Jupiter orbiting the star HIP 99770, which is around twice as massive as our sun.  Direct imaging provides information such as the composition of atmospheres around planets and their temperatures.

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-    This demonstrates that an indirect method sensitive to a planet’s gravitational pull can tell you where to look and exactly when to look for direct imaging.

 

-    “The Transit Method”.  This technique watches for the tiny, telltale dips in a star's brightness caused when a planet crosses (or transits) the star's face, blocking some of its light. NASA's Kepler spacecraft has employed this method to great effect, spotting more than 2,700 potential planets since its March 2009 launch.

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-   Astronomers also look for variations in the timing of a particular planet's transit, because these can reveal the presence of additional worlds orbiting the same star.

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-    “The radial velocity method” picks up on the tiny wobbles an orbiting planet induces in its parent's star's motion toward or away from Earth. This technique is also known as the Doppler method because it measures shifts in the star's light caused by these gravitational tugs.

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-   Several teams of astronomers have discovered many exoplanets using this method and such Earth-based instruments as the HARPS spectrograph, on a telescope at the European Southern Observatory's La Silla Observatory in Chile, and the HIRES spectrograph, on Hawaii's Keck telescope.

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-    “Gravitational Microlensing” , astronomers watch what happens when a massive object passes in front of a star from our perspective on Earth. The nearby object's gravitational field bends and magnifies the light from the distant star, acting like a lens.

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-   This produces a light curve,  a brightening and fading of the faraway star's light over time, whose characteristics tell astronomers a lot about the foreground object, which is often a star. If this star has any planets, these can generate secondary light curves, alerting researchers to their presence.

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-    Gravitational microlensing is less biased toward planets that orbit relatively far from their stars than the transit or radial velocity methods. Researchers have even used it to find so-called "rogue planets," which cruise through the depths of space without a parent star.

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-    Direct Imaging.  Powerful telescopes get actual images of distant worlds, using instruments called coronagraphs to block out the overwhelming glare of their parent stars.  NASA's Hubble Space Telescope has spotted planets by direct imaging, as have Hawaii's Keck Observatory, the European Southern Observatory's Very Large Array in Chile and several other telescopes.

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-    Pulsar Timing,  is specific to planets around pulsars, tiny, superdense remnants of exploded stars that emit radio waves at regular intervals as they rotate.  Anomalies in the timing of these radio pulses can reveal the presence of orbiting planets. The first worlds ever discovered beyond our solar system were found using this method back in 1992.

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-   Harnessing Special Relativity, in this new technique, astronomers watch for a star to brighten as it's tugged by an orbiting planet, causing photons to "pile up" in energy and light to be focused in the direction of the star's motion due to relativistic effects.

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-    The planet Kepler-76b (also known as "Einstein's planet") was discovered via this method, then confirmed by radial velocity measurements. Astrometry relies on the ultraprecise tracking of a star's movements on the sky to spot the gravitational tugs of orbiting planets. (It's similar in principle to the radial velocity method but doesn't measure the Doppler shifts in a star's light.)

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-    Scientists have searched for alien planets using astrometry for decades, with very limited (and debatable) success. But the European Space Agency's Gaia mission, set to launch in October 2013, could spot tens of thousands of exoplanets using the technique.

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                   April 21, 2023     EXOPLANETS  -  discoverring planets around stars?            3968                                                                                                                        

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--------------------- ---  Friday, April 21, 2023  ---------------------------

 

 

 

 

         

 

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