The Role of Ejecta in the Small Crater Populations on the Mid-Sized Saturnian Satellites

We find evidence that crater ejecta play an important role in the small crater populations on the Saturnian satellites, and more broadly, on cratered surfaces throughout the Solar System. We measure crater populations in Cassini images of Enceladus, Rhea, and Mimas, focusing on image data with scales less than 500 m/pixel. We use recent updates to crater scaling laws and their constants to estimate the amount of mass ejected in three different velocity ranges: (i) greater than escape velocity, (ii) less than escape velocity and faster than the minimum velocity required to make a secondary crater (v_min), and (iii) velocities less than v_min. Although the vast majority of mass on each satellite is ejected at speeds less than v_min, our calculations demonstrate that the differences in mass available in the other two categories should lead to observable differences in the small crater populations; the predictions are borne out by the measurements we have made to date. Rhea, Tethys, and Dione have sufficient surface gravities to retain ejecta moving fast enough to make secondary crater populations. The smaller satellites, such as Enceladus but especially Mimas, are expected to have little or no traditional secondary populations because their escape velocities are near the threshold velocity necessary to make a secondary crater. Our work clarifies why the Galilean satellites have extensive secondary crater populations relative to the Saturnian satellites. The presence, extent, and sizes of sesquinary craters (craters formed by ejecta that escape into temporary orbits around Saturn before re-impacting the surface) is not yet well understood. Finally, our work provides further evidence for a "shallow" size-frequency distribution (slope index of ~2 for a differential power-law) for comets a few km diameter and smaller. [slightly abbreviated]Comment: Submitted to Icarus. 77 double-spaced pages, including 25 figures and 5 table

Distant Secondary Craters and Age Constraints on Young Martian Terrains

Are small (less than approx. 1 km diameter) craters on Mars and the Moon dominated by primary impacts, by secondary impacts of much larger primary craters, or are both primaries and secondaries significant? This question is critical to age constraints for young terrains and for older terrains covering small areas, where only small craters are superimposed on the unit. If the martian rayed crater Zunil is representative of large impact events on Mars, then the density of secondaries should exceed the density of primaries at diameters a factor of ~1000 smaller than that of the largest contributing primary crater. On the basis of morphology and depth/diameter measurements, most small craters on Mars could be secondaries. Two additional observations (discussed below) suggest that the production functions of Hartmann and Neukum predict too many primary craters smaller than a few hundred meters in diameter. Fewer small, high-velocity impacts may explain why there appears to be little impact regolith over Amazonian terrains. Martian terrains dated by small craters could be older than reported in recent publications

Uutta elämää odotellessa : Teuvan äitiysneuvolan perhevalmennuskansion päivittäminen ja uudistaminen PowerPoint- esityksen muotoon

Perhe- ja synnytysvalmennuksen sisältö vaihtelee paljon eri kunnissa. Sosiaali- ja terveysministeriön julkaisussa, Seksuaali- ja lisääntymisterveyden edistäminen toimintaohjelma 2007-2011, on suositukset siitä mitä aihealueita valmennuksessa tulisi käsitellä. Opinnäytetyön tarkoituksena on tarjota tietoa perhevalmennuksesta ja sen sisältöalueista sekä toimia liitteenä olevan PowerPoint –esityksen tukena. Opinnäytetyön teoriaosa käsittelee perhevalmennusta, synnytystä, kivunlievitystä, erilaisia synnytysoperaatioita ja imetystä. Lisäksi teoriaosuudessa perehdytään raskausajan muutoksiin naisessa, miehessä ja parisuhteessa. Alan oppikirjojen lisäksi teoriaosuudessa on käytetty aiheeseen liittyviä tutkimuksia. PowerPoint –esitys sisältää kolme eri valmennustuntia. Esitys on tehty Teuvan äitiysneuvolan kätilön toiveiden perusteella ja siinä on teoriatiedon lisäksi paljon kuvia Seinäjoen keskussairaalan synnytyssalista. Jatkossa olisi hyvä tutkia perhe- ja synnytysvalmennuksen eroavaisuuksia ja toteutumista esimerkiksi muutaman kunnan/kaupungin välillä. Esite, joka kertoisi raskausajan muutoksista naisessa, miehessä ja parisuhteessa olisi myös tarpeellinen, koska tietoa näistä asioista löytyi melko niukasti.Prenatal training varies a lot between municipalities. Social and Health Ministry's publication, Promotion of sexual and reproductive health. Action programme 2007-2011., includes recommendations of which areas should prenatal training consist of. The goal of this bachelor' thesis is to offer information about prenatal training and different areas of it, and be a supplement to the PowerPoint presentation. The theoretical part includes prenatal training, labour, pain relief, different kinds of labour (caesarean section, vacuum extraction, forceps delivery) and breastfeeding. Theoretical part also includes the changes in woman, man and relationship during pregnancy. Not only books, but also researches associate with this subject have been used. PowerPoint presentation consists of three different prenatal training lessons. The presentation has been created based on the wishes of the midwife of Teuva maternal clinic and in addition to the theoretical part there are a lot of pictures from the delivery room in Seinäjoki central hospital. In the future it would be good to research differences and actualization in prenatal training for example between few municipalities/cities. A brochure of changes in woman, man and relationship during pregnancy would also be useful, because there is only a little information about this.Liitteenä kolme perhevalmennustuntia PowerPoint- muodoss

Young Martian crater Gratteri and its secondary craters

International audienceIn response to questions that have been raised about formation and effects of secondary craters on crater chronometry techniques, we studied properties of the secondary crater field around the young Martian primary ray crater Gratteri (diameter 7km). The crater has an estimated age of 1 to 20Myr, based on counts of small craters on flat interior surface, consistent with a likely age for a young crater its size (Hartmann et al., 2010). The following are among our findings: (1) We identify an unusual class of craters we call rampart secondaries which may suggest low-angle impacts. (2) We measure size distributions of secondaries as a function of distance from Gratteri and used these data to reconstruct the mass-velocity distribution of ejecta blasted out of Gratteri. Our data suggest that crater density in rays tends to peak around 120-230km from Gratteri (roughly 20-30D) and reaches roughly 30-70 times the interray crater density. (3) Comparable total numbers of secondaries form inside rays and outside rays, and about half are concentrated in clusters in 2% of the area around Gratteri, with the others scattered over 98% of the area out to 400km away from Gratteri. (4) In the old Noachian plains around Gratteri, secondaries have minimal effect on crater chronometry. These results, along with recently reported direct measurements of the rate of formation of 10m to 20m primaries on Mars (Daubar et al., 2013), tend to negate suggestions that the numbers and/or clustering of secondaries destroy the effectiveness of crater counting as a chronometric tool