On this day...

http://earthsky.org/space/what-is-the-tunguska-explosion

On June 30, 1908, an explosion over Siberia killed reindeer and flattened trees. Scientists now believe it was a small comet or asteroid.

In a remote part of Russia, a fireball was seen streaking across the daytime sky. Within moments, something exploded in the atmosphere above Siberia’s Podkamennaya Tunguska River in what is now Krasnoyarsk Krai, Russia.

This event – now widely known as the Tunguska event – is believed to have been caused by an incoming meteor or comet, which never actually struck Earth but instead exploded in the atmosphere, causing what is known as an air burst, three to six miles (5–10 kilometers) above Earth’s surface.

The explosion released enough energy to kill reindeer and flatten trees for many kilometers around the blast site. But no crater was ever found.

Ten Thousandth Near-Earth Object Discovered

From NASA.

June 25, 2013: More than 10,000 asteroids and comets that can pass near Earth have now been discovered. The 10,000th near-Earth object, asteroid 2013 MZ5, was first detected on the night of June 18, 2013, by the Pan-STARRS-1 telescope, located on the summit of the Haleakala crater on Maui. Managed by the University of Hawaii, the PanSTARRS survey receives NASA funding.

Asteroid 2013 MZ5 as seen by the University of Hawaii's PanSTARR-1 telescope. In this animated gif, the asteroid moves relative to a fixed background of stars. Image credit: PS-1/UH

"Finding 10,000 near-Earth objects is a significant milestone," said Lindley Johnson, program executive for NASA's Near-Earth Object Observations (NEOO) Program at NASA Headquarters. "But there are at least 10 times that many more to be found before we can be assured we will have found any and all that could impact and do significant harm to the citizens of Earth."

Visions of the Universe

In a new exhibition - Visions of the Universe - at the National Maritime Museum in London, more than 100 awe-inspiring views of space are on show, exploring the development of telescopy, photography, and our understanding of our place in the Universe.

Star cluster Pismis 24
Photographed by the Hubble Space Telescope, 2006 (NASA)

More at the BBC.

First Woman In Space

50 years ago today Valentina Vladimirovna Tereshkova (Russian: Валенти́на Влади́мировна Терешко́ва; born 6 March 1937) was the first woman in space.

She is a retired Soviet cosmonaut and Engineer, and the first woman to have flown in space, having been selected from more than four hundred applicants and five finalists to pilot Vostok 6 on 16 June 1963. 

In order to join the Cosmonaut Corps, Tereshkova was only honorarily inducted into the Soviet Air Force and thus she also became the first civilian to fly in space. During her three-day mission, she performed various tests on herself to collect data on the female body's reaction to spaceflight.

Thanks to Wikipedia 

Explaining the Topography of Mars

June 11, 2013: NASA research indicates hunks of frozen carbon dioxide, dry ice, may glide down some Martian sand dunes on cushions of gas similar to miniature hovercraft, plowing furrows as they go.

"I have always dreamed of going to Mars," said Serina Diniega, a planetary scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif., and lead author of a report published online by the journal Icarus. "Now I dream of snowboarding down a Martian sand dune on a block of dry ice."

Watch the experimental report at http://youtu.be/mNXBfz1iVzc

This image from the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter is an example of a type called "linear gullies," which may be explained by slabs of dry ice gliding down the slopes of sand dunes. Image credit: NASA/JPL-Caltech/Univ. of Arizona

Researchers deduced this process could explain one enigmatic class of gullies seen on Martian sand dunes by examining images from NASA's Mars Reconnaissance Orbiter (MRO) and performing experiments on sand dunes in Utah and California.
The hillside grooves on Mars, called linear gullies, show relatively constant width -- up to a few yards, or meters, across -- with raised banks or levees along the sides. Unlike gullies caused by water flows on Earth and possibly on Mars, they do not have aprons of debris at the downhill end of the gully. Instead, many have pits at the downhill end.

Thanks and more at NASA.

Most “super” supermoon of 2013

Full moon falls on June 23, 2013 at 11:32 UTC. This full moon is not only the closest and largest full moon of the year. It also presents the moon’s closest encounter with Earth for all of 2013. The moon will not be so close again until August, 2014.

Astronomers call this sort of close full moon a perigee full moon. The word perigee describes the moon’s closest point to Earth for a given month. Two years ago, when the closest and largest full moon fell on March 19, 2011, many used a term we’d never heard before: supermoon. Last year, we heard this term again to describe the year’s closest full moon on May 6, 2012. Now the term supermoon is being used a lot. Last month’s full moon – May 24-25, 2013 – was also a supermoon. But the June full moon is even more super! In other words, the time of full moon falls even closer to the time of perigee, the moon’s closest point to Earth. The crest of the moon’s full phase in June 2013, and perigee, fall within an hour of each other.

 Did you know?

- the tides will be higher/lower at perigee

- an astrologer came up with the term supermoon

- each full moon has a name
- this month is know as Rose Moon, Flower Moon or Strawberry Moon in the Northern Hemisphere




More here. Thanks to EarthSky News.