Today is Memorial Day in the United States, a day set aside to honor our men and women who died while in military service since the time of U.S. Civil War. In Afghanistan over 50 U.S. soldiers have been killed in just the past month, including 24-year old Marine Cpl. Jacob Leicht, who became the 1,000th serviceman killed in Afghanistan since 2002. As the fighting season begins, Taliban militants have recently mounted several bold attacks and coalition efforts to "clear, hold and build" areas in the south have been slowed during the "hold" phase, as Afghan government capacity remains small. Collected here are images of the country and conflict over the past month, part of an ongoing monthly series on Afghanistan. (42 photos total)

Fill a lightweight material with hot air, helium or hydrogen, and you have a vessel that floats in the air. People around the world use balloons, blimps and airships for transportation, to conduct research, to deliver messages, to protest, and - mostly - for having fun. Collected here are recent photographs of balloons of all shapes, sizes and purposes - ranging from a child's toy to a football-field-sized research instrument, and much in between. (31 photos total)

Two hundred years ago, in Buenos Aires (then capital of a Spanish colony), a week-long series of revolutionary events took place, known as the Revolucion de Mayo, which set in motion events that led to Argentina's eventual declaration of independence from Spain in 1816. This week, millions of Argentinians, their neighbors and foreign dignitaries gathered in Buenos Aires to celebrate their bicentennial with lavish parades festivals and performances. Collected here are recent scenes from Argentina as its citizens commemorate 200 years of eventful history. (30 photos total)

Over one month after the initial explosion and sinking of the Deepwater Horizon oil rig, crude oil continues to flow into the Gulf of Mexico, and oil slicks have slowly reached as far as 12 miles into Louisiana's marshes. According to Louisiana Governor Bobby Jindal, more than 65 miles of Louisiana's shoreline has now been oiled. BP said it will be at least Wednesday before they will try using heavy mud and cement to plug the leak, a maneuver called a "top kill" that represents their best hope of stopping the oil after several failed attempts. Based on low estimates, at least 6 million gallons of crude have spewed into the Gulf so far - though some scientists have said they believe the spill already surpasses the 11 million-gallon 1989 Exxon Valdez oil spill off Alaska as the worst in U.S. history. (39 photos total)

While we humans carry on with our daily lives down here on Earth, perhaps stuck in traffic or reading blogs, or just enjoying a Springtime stroll, a school-bus-sized spacecraft called Cassini continues to gather data and images for us - 1.4 billion kilometers (870 million miles) away. Over the past months, NASA's Cassini spacecraft has made several close flybys of Saturn's moons, caught the Sun's reflection glinting off a lake on Titan, and has brought us even more tantalizing images of ongoing cryovolcanism on Enceladus. Collected here are a handful of recent images from the Saturnian system. (30 photos total)

Earlier today, soldiers from the Thai Army broke down barricades and entered the fortified camp occupied by anti-government Red Shirt protesters for the past several weeks in downtown Bangkok. Several clashes took place, and Red Shirt leaders announced to their followers that they were surrendering to police as the soldiers approached. Many protesters dispersed, but some continued to battle with grenades, guns, slingshots and fire, setting as many as 20 locations ablaze in central Bangkok. At this stage, it is unclear how many have been killed or injured, but at least five are known to have died, with dozens more injured. Thai authorities have imposed a curfew as they battle fires, process detainees and clear the rest of the Red Shirt encampment. (39 photos total)

On May 18th, 1980, thirty years ago today, at 8:32 a.m., the ground shook beneath Mount St. Helens in Washington state as a magnitude 5.1 earthquake struck, setting off one of the largest landslides in recorded history - the entire north slope of the volcano slid away. As the land moved, it exposed the superheated core of the volcano setting off gigantic explosions and eruptions of steam, ash and rock debris. The blast was heard hundreds of miles away, the pressure wave flattened entire forests, the heat melted glaciers and set off destructive mudflows, and 57 people lost their lives. The erupting ash column shot up 80,000 feet into the atmosphere for over 10 hours, depositing ash across Eastern Washington and 10 other states. Collected here are photos of the volcano and its fateful 1980 eruption. [Editor's note: I lived in Eastern Washington at the time, and have strong memories of this event, the dark skies, the strangeness of it all. I can't believe it's been 30 years. -Alan] (37 photos total)

The Red Shirt political protest in Bangkok, Thailand has been active for nearly two months now, and has entered a new, deadly phase in the past week, with at least 36 of the total 60 deaths occurring in just the last few days. Anti-government protesters have barricaded themselves against government troops and the Thai army has declared certain protest areas to be "Live Fire Zones". A state of emergency is in effect, covering 17 provinces in the country, as protesters have refused orders to leave, and news just emerged that a renegade general who supported the Red Shirts, Khattiya Sawatdithol, died today from a gunshot wound he suffered on May 13th. Collected here are photos of the recent turmoil in central Bangkok. (39 photos total)

First launched twenty-five years ago in October of 1985, NASA's Space Shuttle Atlantis is scheduled for its 32nd and final launch this afternoon (at 2:20pm ET). This launch - one of only three remaining missions left in NASA's Shuttle program - will deliver an Integrated Cargo Carrier and a Russian-built Mini Research Module to the International Space Station. Collected here are a series of photographs of Atlantis' recent activity, as it descended from orbit last November, landed, and was processed and prepped for today's final launch. (42 photos total)

In the three weeks since the April 20th explosion and sinking of the Deepwater Horizon oil rig in the Gulf of Mexico, and the start of the subsequent massive (and ongoing) oil leak, many attempts have been made to contain and control the scale of the environmental disaster. Oil dispersants are being sprayed, containment booms erected, protective barriers built, controlled burns undertaken, and devices are being lowered to the sea floor to try and cap the leaks, with little success to date. While tracking the volume of the continued flow of oil is difficult, an estimated 5,000 barrels of oil (possibly much more) continues to pour into the gulf every day. While visible damage to shorelines has been minimal to date as the oil has spread slowly, the scene remains, in the words of President Obama, a "potentially unprecedented environmental disaster." (40 photos total)

With the disastrous oil spill in the Gulf of Mexico still unfolding, concerns over threats to wildlife have brought animals into the news quite a bit lately. From the oil spill, to preservation efforts, to zoo developments, pampered pets, harsh environments, invasive fish, a surfing alpaca and more, collected here are a handful of recent photographs of animals and our interactions with them, as companions, caretakers, observers, and stewards. (40 photos total)

A few small announcements and some stats as Big Picture nears its two-year anniversary (normal full entry to come shortly).

1) There is now an official iPhone/iPod Touch app for Big Picture (link will attempt to launch iTunes). An iPad app is still in the works, but will be coming soon (yes, we have heard the requests from many of you, thank you).

2) We've changed the header and icons slightly, looking for a more cohesive presence across the web.

3) Big Picture Archives are now a little easier to find and navigate now, From May of 2008 to May of 2010, navigate by using the "archives" dropdown in the upper navigation, or, in the archives, clicking on the links to "Next" or "Previous" months.

4) For those that don't already know, The Big Picture now has a presence on Twitter at @big_picture, and on Facebook

more inside...

Last Friday, April 30th, was the 35th anniversary of the Fall of Saigon and the end of the Vietnam War, and last Tuesday, May 4th, was the 40th anniversary of the shooting of protesting students at Kent State University. The Vietnam War and America's involvement in it affected the lives of millions for well over a decade, exacting a massive human cost with millions of deaths and countless injuries - both physical and mental - that plague many of those involved to this day. United States military involvement and troop strength grew rapidly after 1964 - at its highest level in 1968, with over 500,000 troops on the ground. The Vietnam Veterans Memorial in Washington, D.C. now bears the engraved names of 58,267 of those troops. It's nearly impossible to encapsulate an event of such scale in a handful of photographs, but here, 35 years after the end of the conflict, is my attempt. (47 photos total)

Last weekend, powerful thunderstorms drenched Tennessee, Kentucky and Mississippi, dumping over 13 inches of rain on the region in two days. Creeks, lakes and rivers swelled with the rainwater, overflowing their banks, washing away roads, and causing the deaths of at least 24 people so far. The Cumberland River, which winds through downtown Nashville, Tennessee, crested Monday at 51.9 feet, 12 feet above flood stage, spilling into the city and surrounding neighborhoods. As the waters are now receding, cleanup and recovery begins, as municipal workers begin to repair power supplies and water treatment plants, and residents return to their homes to recover what they can. (38 photos total)

A recent Pentagon report on the situation in Afghanistan over the past 6 months gives the impression that while things aren't necessarily getting any worse, they are far from improving. Afghan citizens, when polled, showed only limited support for their government, and a slight majority placed the blame for instability on Taliban forces. There remains a heavy reliance on international forces to provide security, training and equipment. As of March 31st, there were approximately 133,500 foreign troops on the ground in Afghanistan - 87,000 U.S. forces and 46,500 international forces. This month also saw the departure of a U.S. military presence from Afghanistan's notorious Korengal Valley, a small, isolated, patch of difficult terrain where 42 soldiers lost their lives over the past five years. NATO is calling the move a "realignment", focusing efforts on more-populated areas. Collected here are images of the country and conflict over the past month, part of an ongoing monthly series on Afghanistan. (43 photos total)