Stunning Images From ESA of Mars' Labyrinth of the Night (Noctis Labyrinthus)

link.

Phobos and Mars Courtesy of Mars Express

The Origin of Phobos' Grooves

Character and origin of Phobos’ grooves

Authors:

Murray et al

Abstract:

Phobos’ parallel grooves, which are such a striking feature of its surface, have attracted interest since their discovery on Viking images in 1976 ( Veverka and Duxbury, 1977), but their origin is still in dispute today. The great increase in knowledge of Phobos’ surface features effected by images from the High Resolution Stereo Camera (HRSC) onboard the E.S.A. Mars Express spacecraft has clearly demonstrated that only one hypothesis can seriously be upheld: that the grooves are chains of secondary impacts resulting from primary impact events on Mars ( Murray and Iliffe, 2011). But even this hypothesis has recently been questioned from a ballistic standpoint ( Ramsley and Head, 2013) mainly using estimated data for the grooves themselves. In the present paper we present summaries of extensive new measurements of groove sizes, pit separations, groove family parameters and geographical distribution. We also re-examine their unique characteristics, and present a review of past ideas. But we concentrate on extending and refining the work of Ramsley & Head using the new measurements, and the much-improved geodetic data from Mars Express (Willner et al., this issue). We find that the total mass of Mars ejecta required to form all the observed grooves on Phobos is between 2.0 × 109 and 2.7 × 1010 kg, and that the total mass of impact ejecta from all Mars craters between 19 and 384 km diameter likely to hit Phobos (in its present orbit) at sufficient velocity to form all the grooves is one or two orders of magnitude greater than this. The larger available ejecta mass from Mars is due to several factors, including the fact that Phobos is known to have orbited Mars at a greater distance at the time when the grooves were formed. A new rigorous celestial mechanical analysis of the transfer of ejecta from Mars to Phobos is presented, including N-body calculations that model not only the gravitational interaction of Mars, but also of Phobos and up to several hundred individual ejecta particles. This allows us to model the possible source areas on Mars of all observed groove families, and to conclude that more than one groove family may have been formed by different batches of ejecta from the same Mars impact event, and that the total number of Mars impact events responsible for creating the grooves may have been less than 10. The N-body calculations also allow us to model the complex gravitational interactions between Mars ejecta particles, and thus to assess the contrast in groove morphometry between those families centred on the sub-Mars and anti-Mars hemispheres.

New Model Suggests Mars Express Derived Scenarios Underestimate Carbon, Oxygen Lost

Hot oxygen and carbon escape from the martian atmosphere

Authors:

Gröller et al

Abstract:

The escape of hot O and C atoms from the present martian atmosphere during low and high solar activity conditions has been studied with a Monte-Carlo model. The model includes the initial energy distribution of hot atoms, elastic, inelastic, and quenching collisions between the suprathermal atoms and the ambient cooler neutral atmosphere, and applies energy dependent total and differential cross sections for the determination of the collision probability and the scattering angles. The results yield a total loss rate of hot oxygen of View the MathML source during low and high solar activity conditions and is mainly due to dissociative recombination of O2+ and CO2+. The total loss rates of carbon are found to be 0.8 and View the MathML source for low and high solar activity, respectively, with photodissociation of CO being the main source. Depending on solar activity, the obtained carbon loss rates are up to ∼40 times higher than the CO2+ ion loss rate inferred from Mars Express ASPERA-3 observations. Finally, collisional effects above the exobase reduce the escape rates by about 20–30% with respect to a collionless exophere.

Mars Express Flyover of Mars

Mars Express' Investigations into the Martian Moons of Phobos and Deimos

Mars Express Investigations of Phobos and Deimos

Authors:

O. Witasse et al (too many again)

Affiliations:

no way.

Abstract:

The Mars Express mission was launched in June 2003 and was inserted into orbit around Mars in December 2003. Its main objective is to study the Mars' subsurface, surface, atmosphere and interaction with the solar wind. A secondary objective is to study the martian moons, in particular the largest one Phobos, thanks to a near polar and elliptical orbit which allows the spacecraft to perform close flybys about every five months. The Mars Express data not only consist of high-resolution 3D color images, but also astrometric images, spectra from 0.18 to 20 μm, radar echoes, Doppler signals from gravity experiments, and ion data. A new view of the moons has emerged from this data set, favoring now the idea that they are not captured asteroids, but rather the result of a re-accretion following a major impact on Mars. This unique set of data is available in the ESA Planetary Science Archive (PSA) and mirror imaged in the NASA Planetary Data System (PDS). This paper presents an overview of the Mars Express Phobos flybys, the specificities of their operations and the scientific achievements.

Kasei Valles: One of the Great Floods of Mars

Dramatic flood events carved this impressive channel system on Mars covering 1.55 million square kilometres, shown here in a stunning new mosaic from ESA’s Mars Express.

The mosaic, which features the spectacular Kasei Valles, comprises 67 images taken with the spacecraft’s high-resolution stereo camera and is released during the week of the 10th anniversary of the spacecraft’s launch to the Red Planet.

Kasei Valles is one of the largest outflow channel systems on Mars – from source to sink, it extends some 3000 km and descends by 3 km in altitude. The scene covered in the mosaic spans 987 km north–south (19–36°N) and 1550 km east–west (280–310°E).

The channel originates beyond the southern edge of this image near Valles Marineris, and empties into the vast plains of Chryse Planitia to the east.

Kasei Valles splits into two main branches that hug a broad island of fractured terrain – Sacra Mensa – rising 2 km above the channels that swerve around it. While weaker materials succumbed to the erosive power of the fast-flowing water, this hardier outcrop has stood the test of time.

Slightly further downstream, the flood waters did their best to erase the 100 km-wide Sharonov crater, crumpling its southern rim. Around Sharonov, many small streamlined islands form teardrop shapes rising from the riverbed, carved as water swept around these natural obstacles.

The region between Sacra Mensa and Sharonov is seen in close-up detail in the perspective view below, looking downstream from the northern flank of Kasai Valles.