Tag: Spaceflight

In October 2014, I wrote about comet Sliding Spring and it’s close approach to Mars as it swung through the solar system.

The comet had been identified as coming from the Oort cloud (or the Öpik–Oort cloud, to give proper recognition both astronomers who initially and independently postulated its existence), a spherical cloud of debris left-over from the creation of the solar system, occupying a huge area starting some 2,000-5,000 AU (2,000 to 5,000 times the distance from the Earth to the Sun) and extending out to around 50-100,000 AU – or about one light year away.

There is nothing odd about comets from the Oort cloud per se, but Sliding Spring appeared to be making its very first journey into the inner solar system, and so astronomers were keen to try to study it as best they could. Given the close pass at Mars, the vehicles on and orbiting that planet stood to have something of a grandstand view of things – providing certain precautions were taken, as I noted at the time.

Now data released by NASA shows that the comet’s flight past Mars did result in something very unusual: the comet’s tail, which brushed the Martian atmosphere, resulted in a “rain of metal” over the planet.

The data was obtained by NASA’s Mars Atmosphere and Volatile EvolutioN Mission (MAVEN), which at the time of the comet’s passage was so recent an arrival at Mars, that all its instruments hadn’t been fully commissioned. Hence, in part, the delay in releasing the data – NASA wanted to be sure MAVEN was recording things accurately.

According to MAVEN, the direct detection of sodium, magnesium, aluminium, chromium, nickel, copper, zinc, iron and other metals high in the Martian atmosphere can be linked directly to material sloughing off of the comet as it passed.

“This must have been a mind-blowing meteor shower,” said Nick Schneider of the Laboratory of Atmospheric and Space Physics at the University of Colorado, commenting on the data returned by the orbiter. Such is the strength of the signal of magnesium and iron measurements, the hourly meteor rate overhead on Mars must have been tens of thousands of “shooting stars” per hour over a period of many hours.

“I’m not sure anyone alive has ever seen that,” Schneider added, “and the closest thing in human history might the the 1833 Leonids shower.” The metal ions were the remains of pebbles and other pieces shed from the comet that burned up, or “ablated” into individual atoms as they struck the Martian atmosphere at 56 kilometres per second (125,000 miles per hour).

What is particularly important about the event is that as scientists know the source of the dust particles, it’s speed, and key information about Mars’ upper atmosphere, it is possible to learn more about Mars’ ionosphere, the comet’s composition, and even the workings of Earth’s ionosphere when it is hit by comet or asteroid debris.

Impact Glass

There is glass on Mars, and it might just be the ideal place in which to find any evidence of past microbial life.

The type of glass in question is referred to as “impact glass”, and is formed as a result of the heat generated by the impact of a meteorite melts the surrounding rock into glass. when a meteorite strikes the surface of a planet or moon, melting the surrounding rock into glass, preserving and organic matter that existed on or in the rock prior to the meteorite impact occurring.

In 2014, a research team examining impact glass formed millions of years ago as a result of meteorite strikes in Antarctica form found organic molecules and plant matter within the glass. Their work spurred a group of planetary science graduates at Brown University, Rhode Island, to simulate the spectral composition of possible Martian impact glass by using chemicals, compounds and powders matching those known to compose the surface material on Mars, and then melting the mix at high temperatures to form glass, which they then subjected to spectrographic analysis.

The team then compared the results of their analysis with spectral analyses of the surface of Mars carried out by the Imaging Spectrometer aboard NASA’s Mars Reconnaissance Orbiter (MRO) – and found a very similar spectral signature in areas where such impact glass would be expected to form, such as around the central peaks of craters caused by meteorite impacts.

Continue reading “Space Sunday: metal rain and glass on Mars, HoloLens into orbit” →

ESA’s Philae lander, which as I reported a week ago, resumed contact with Earth via its “Parent”, Rosetta, after seven months in hibernation, continues to return data to Earth from comet 67P/Churyumov–Gerasimenko (67P/C-G) as it continues towards the Sun.

Friday, June 19th, marked the latest transmission from Philae, which is about the size of a domestic washing machine, bringing the total of communications with mission control in Germany to 3 since the lander managed to re-establish its link with Rosetta.

Communications are sporadic because it is still not entirely clear where Philae is sitting on the comet, having bounced across the surface following its initial touch-down in November 2014. This, and Rosetta’s science-focused orbit around the comet means that there can be extended periods of several days between the times when both spacecraft and lander are suitably aligned to allow communications to take place.

The Friday communication lasted 19 minutes, and allowed the lander to return a further 185 packets of data to Earth. The data gave additional confirmation that Philae is in good health and in an environment which means it should be quite comfortable for a good while – thus increasing the chances of it resuming its science activities.

“Among other things, we have received updated status information,” Michael Maibaum, a systems engineer at the DLR Lander Control Centre in Cologne, reported following the Friday contact. “At present, the lander is operating at a temperature of zero degrees Celsius, which means that the battery is now warm enough to store energy. This means that Philae will also be able to work during the comet’s night, regardless of solar illumination.”

The three communications so far received mean that the mission team now have sufficient data to be able to more accurately position Rosetta so that it can continue with its primary science mission while being better placed to improve radio visibility between it and the lander’s estimated location. The first set of commands for the spacecraft to start adjusting its orbit were uploaded on Wednesday, June 17th, and and further set of instructions were uploaded on Saturday, June 20th. The aim is to close the distance between Rosetta and the comet to 177 kilometres within an orbit that will allow the orbiter to be above Philae’s horizon more regularly than is currently the case.

Pluto’s Gentle Fade In

NASA’s New Horizons mission to the Pluto-Charon system is now less than a month from its point of closest approach, which will occur on July 14th, 2015. As the fast-moving spacecraft closes on the two planetoids, the images it is returning to Earth of Pluto are starting to show tantalising splotches of dark across the planetoid’s surface, the first hints of landforms.

The pictures are still nowhere near being as clear as they should be in the days immediately prior to and following the point of closest approach, but they are still nevertheless interesting; in April 2015, New Horizons images what appears to be a polar ice cap on Pluto, so scientists are curious to what else might be revealed.

At the time of closest approach, New Horizons should be within 10,000 kilometres (6,200 miles) of Pluto and around 27,000 kilometres (17,000 miles) of Charon. The fly-by of Pluto should allow the main telescope camera system on the vehicle to take selected high-resolution images of Pluto at a scale of 50 metres / pixel. It is hoped that the average resolution of daylight images captured of Pluto will be around 1.6 km (1 mile) resolution, and will allow the composition of 4-colour maps of the surface.

From around 3.2 days before closest approach, long-range imaging will be used to map both worlds to a resolution of around 40 kilometres (25 miles).  New Horizons will also attempt to gather data on the nature of any atmosphere present on Pluto and seek evidence of any cryovolcanism which might be occurring or surface feature changes which might be attributable to snowfall or similar.

Titan: Even More In Common

There are only two places in our solar system known of have rainfall, rivers and oceans, as well as a thick atmosphere, rocky ground and plate tectonics. They are Earth and Saturn’s huge moon, Titan. Now the joint ESA / NASA Cassini mission has revealed Titan shares something else with Earth: polar “winds” that suck gasses out of its atmosphere and into space.

Titan’s atmosphere has around a 50% higher surface pressure than Earth’s, and is comprised mainly of nitrogen and methane, and is rich in hydrocarbons, which also exist in lakes, reivers and seas on the surface of the planet.

Several years ago Cassini, which has been orbiting in orbit around Saturn for over a decade, revealed that around seven tonnes of hydrocarbons and nitriles were being lost every day from the upper layers of Titan’s atmosphere, but the mechanism causing the loss remained unknown until CAPS, the instrument which first recorded the loss recorded the “wind” in action.

Essentially, sunlight striking the upper layers of Titan’s atmosphere ejects negatively charged electrons out of the hydrocarbon and nitrile molecules resting there. These electrons are then drawn away along Saturn’s magnetic field, generating their own electrical field strong enough to “pull” the positively charged particles left behind by the formation of the original electrons out of the atmosphere along with them.

On Earth, this process charges particles in the atmosphere and draws them up along the planet’s magnetic field, where they can escape at the poles, and the same thing is happening on Titan. The discovery has lead to speculation that similar processes might be at work on Mars and Venus.

Continue reading “Space Sunday: Philae, Titan and Pluto, oh my!” →

The joint ESA / NASA Dawn mission to study two of the solar system’s three “protoplanets” located in the asteroid belt between the orbits of Mars and Jupiter, continues to intrigue scientists.

Launched in September 2007, and costing US $446 million, Dawn is part of a broader effort to better understand the origins of the solar system and how the planets actually formed; all of which might give us greater understanding of how life arose here on Earth.

The mission has been relatively low-key when compared to the likes of NASA’s MSL rover on Mars or Europe’s Rosetta mission to comet 67P/C-G and NASA’s other mission to tiny world. New Horizons, but the Dawn spacecraft and mission are quite remarkable. The little spacecraft is use ion propulsion to enter orbit around a planetary body and is the first to orbit a dwarf planet and, since its arrival in orbit around Ceres, the first spacecraft from Earth to visit that tiny dwarf planet and the first mission to orbit two separate extraterrestrial bodies.

Dawn arrived at Ceres in March 2015, after a 2.5 year transit flight from Vesta, its first destination, where it spent 14 months in orbit following its arrival there in July 2011. Because of their relative size – Ceres accounts for around one-third of the total mass of the asteroid belt –  both of these airless, rocky bodies are regarded as dwarf planets, rather than “simple” asteroids.  However, they are both very different bodies to one another.

With a diameter of 525 kilometres (326 miles), Vesta is the smaller of these two worldlets, and is technically regarded as water-poor achondritic asteroid comprising a tenth of the mass of the asteroid belt. Its density is lower than the four inner planets of the solar system but higher than most of the moons and asteroids.

Ceres, with a diameter of 950 kilometres (590 miles), is just 2.5 times smaller than distant Pluto, the target of the New Horizons mission. Its spectral characteristics suggest a composition similar to that of a water-rich carbonaceous chondrite. Like most of the material within the asteroid belt, it formed very early in the history of the Solar System, thereby retaining a record of events and processes from the time of the formation of the terrestrial planets.

Since arriving in orbit around Ceres, Dawn has returned some intriguing images of apparent bright spots within a crater. These were first seen in late 2014, as Dawn made its initial approach to Ceres, and have since been imaged on numerous occasions, and have been tracked as Ceres rotates, eliminating them as being imaging artefacts. Studies of much lower resolution images of Ceres taken by the Hubble Space Telescope also reveal these bright spots – although such is the distance of Ceres from Hubble that where they do appear in HST pictures, they are little more than a single bright blob.

The thinking on the bright areas are that they are water ice  or possibly frozen salt deposits – although they could be something more exotic. Over the last two months, Dawn has been able to image the bright areas, which lie in a crater some 92 kilometres (57 miles) across, situation some 19 degrees above Ceres’ equator. On June 6th, 2015, Dawn returned the best images yet of the bright spots, and these have been added to an animation made up of multiple images of Ceres, showing it rotating about its axis.

At the end of June, Dawn will commence a series of manoeuvres which will gently lower its orbit over the period of 6 weeks, allowing it to get much more detailed images of the surface of Ceres and these strange spots. As the images will also be captured from multiple angles, scientists hope they’ll provide sufficient information for the composition of the bright spots to be understood.

Continue reading “Space Sunday: imaging tiny worlds, flying saucers, and a matter of size” →