April 23, 2003: The independent investigation team has all be arrived
at a firm conclusion. A seal on the left wing was struck by foam
during liftoff and fell off the next day, they believe, creating a
gap that let hot gas enter the ship during re-entry. Story

A sort of "black box" recently recovered on the ground reveals that
hot gas penetrated the left wing earlier than previously known. The
newfound data, thought scant, suggests Columbia probably had a
problem before it began re-entry into Earth's atmosphere and that the
problem was likely on or near the leading edge of the left wing,
officials said March 31.

A Florida Today investigation recently showed that NASA fueled and
launched Columbia in weather ripe for producing ice on the external
fuel tank, potentially setting up a situation in which insulation
foam, possibly heavy and laden with ice, might have damaged the craft shortly after liftoff.

Separately, officials have said a mystery object that floated away
from Columbia during its second day in orbit may have had something
to do with the disaster. Some experts speculate the object, which
fell into the atmosphere a couple days later, could have been a heat
protection tile or some other piece of the shuttle, reports
SPACE.com's Leonard David. A data processing issue meant the U.S. Air Force did not recognize the object for what it was and NASA was not informed of it until after the disaster.

The investigation board, meanwhile, said on March 18 that super-
heated air rushing inside the space plane's left wing was now the
leading candidate to explain Columbia's demise.

Meanwhile, lab tests are underway to help determine what might have
caused the breakup. But so far there are no firm results and several
possibilities remain on the table. Even some new scenarios were being
discussed last week.

Investigators have not ruled out pilot error, though there are no
indications that this was the cause. They are also studying
additional stress load experienced on the left side of the shuttle 62
seconds after liftoff. The space plane's age is also being looked
into as a possible factor. [Story on these aspects]

Officials now say that during liftoff, three distinct pieces of
material came off the external fuel tank and may have hit parts of
the left wing (on Feb. 21, they had said at least two pieces, and
possibly three, were involved). Though long said to be insulation
foam, this stuff might also have been ice, a combination of ice and
foam, or possibly material applied under the foam, investigators now
say.

Columbia as it broke apart.

Initial story

Meanwhile, preliminary lab experiments have surprised researchers,
showing that high-speed foam hitting the shuttle wing and its thermal
protection tiles might harm the aluminum structure underneath,
without leaving visible damage at the surface. SPACE.com reported
March 13 that tests are planned for early April to shoot external
tank foam at shuttle wing material.

On March 4, officials announced that melted aluminum was found on
recovered thermal tiles and inside the leading edge of the left wing.
The shuttles' skins are aluminum, protected by the heat-resistant
tiles. Officials said this finding supports the possibility that the
shuttle was destroyed by hot gas that penetrated a damaged spot on
the wing. They have not yet determined, however, how that gas was
allowed entry.

On March 11, investigators explained that when aluminum is vaporized,
as it might have been from hot gas inside the wing or wheel well, its
particles become volatile. Rapid burning of those particles could
behave like a bomb, and might explain one or more of the bright
flashes observed from the ground as the shuttle broke apart.

E-mail exchanges

In late February and early March (2003), NASA detailed how engineers, flight planners and outside contractors debated disaster scenarios that, in retrospect, contained hauntingly accurate aspects. Officials first acknowledged Wednesday, Feb. 26 that engineers had exchanged e-mails during the mission discussing whether damage that might have occurred during liftoff would cause problems during re-entry or landing.

Otherwise, the list of possible answers has grown along with a list
of questions. Even space weather experts are looking over data for
signs that something abnormal might have occurred on Feb. 1 where
solar energy interacts with Earth's atmosphere and magnetic field.

The idea that hot gas entered the shuttle through a breach in the
left wing or wheel well goes back to Feb. 13. Many experts suspected
then that a reinforced carbon-carbon (RCC) panel on the forward edge
of Columbia's left wing was the first major piece to break loose
during re-entry as the shuttle approached the California coast. In a
step-by-step account published Wednesday, Feb. 19, SPACE.com's Jim Banke explains how this might have happened and how a missing panel could have led to the disastrous cascade of events that brought
Columbia down.

The hot gas was likely not "plasma," as had been first reported,
officials said. Hot gas surrounding the shuttle during re-entry had
not yet reached the plasma stage, which would occur lower in the
atmosphere.

The independent investigation board acknowledged late Tuesday, Feb.
18, that the shuttle's problems began when it was over the Pacific
Ocean, well before it broke apart above Texas. Investigators are
gathering data from ground-based "microbarometers," sensors all
across the west that might have detected minute anomalies in
Columbia's movement as the problems developed. The sensors detect
minor changes in air pressure that propagate through the atmosphere.

One of these sensors, in Texas, recorded an explosion equal to a few
pounds of TNT. "Our guess is that it could have been caused by a
rapid decompression, which is what would have happened if you
ruptured the crew compartment,'' said Eugene Herrin, a geophysicist
at Southern Methodist University.

The breach

Outside experts said the shuttle's aluminum skin and overall
construction is not designed to handle an infusion of hot gas, which
can reach temperatures of up to 3,000 degrees and is very expansive.
A 1997 independent report by the National Security Council warned
that a bit of manmade space debris or a natural meteorite could cause
a hole in the vulnerable leading edge of a shuttle wing upon re-
entry, and that the result would be a "blowtorch" effect, leading to
the demise of the craft.

NASA cast some doubt on whether the hot gas -- not yet plasma -- that likely breached Columbia would have had this blowtorch effect.

Shuttles, like all spacecraft, are routinely peppered by meteoroids
the size of sand grains, paint chips, and other debris. The shuttle
is designed, in theory, to handle minor impacts. Heat tiles
sustaining minor damage, typically small divots, are routinely
replaced after flights.

Columbia was the oldest shuttle in the fleet. In the last major
overhaul, done in 2001 by the Boeing Co, the entire shuttle was
inspected for damaged tiles and stress to its aluminum frame and
modifications were made. The independent investigation team is
looking into the details of the overhaul as part of the inquiry but
officials said they are not yet aware of any link to the problems on
the ship's final flight. Columbia flew one successful mission after
the overhaul.

Other scenarios for breaching the shuttle that have not been elimated:

a strike by a meteoroid or space junk,

sabotage

accidentally triggered onboard explosive devices the possibility that

Columbia's waste expulsion system might havedeveloped a chunk of

ice during the flight that could have damaged the wing. The waste vent

is in front of the left wing. It expels urine and excess water created by the

power system. In a 1984 flight, a basketball-sized chunk of ice developed

on Discovery. The crew broke it off prior to re-entry using the shuttle's

robot arm. Columbia did not need the arm for its science mission and so

it was not available.

Earlier in the investigation, it was learned that a military radar
detected some object, which might have been ice, near the shuttle
early in the mission.

Search continues

On March 12, Columbia Accident Investigation Board (CAIB) chairman,
retired Admiral Hal Gehman, said as many as 5,000 people were still
conducting daily searches for debris, though the findings lately have
been mostly small pieces. In all, more than 28,000 bits of debris,
small and large, had been collected as of March 10. Gehman expects
more stuff to turn up when weather improves, when snow melts, and
farmers begin plowing fields.

On Feb. 19, NASA asked for public help in finding debris in Arizona,
Nevada, New Mexico, and Utah. Search teams have had little luck
finding Columbia debris significantly west of Fort Worth, Texas.
Experts in tracking the breakups and paths of space rocks through
Earth's atmosphere have been called in to help determine where debris
might have fallen. The effort is intended to locate possible debris
in the mountains of California that might be among the first telling
pieces to have separated from the shuttle.

Much of the investigation centers on increased heat detected by
sensors in and around the left wing and left wheel well moments
before all contact was lost with Columbia.

After analyzing the data, officials say the first problems were noted
at 8:52 a.m. ET on Feb. 1 in a brake line behind the left wheel well
and a failing sensor on the aircraft's skin, near the rear of the
left wing on the underneath side. A tire in the left wheel well then
showed signs of problems before a pressure gauge failed. By 8:59,
elevated temperatures had been noted in at least four other sensors,
including two on the fuselage, and a handful had gone offline.

Shuttles are not equipped with the "black boxes" that airliners
carrry to store onboard data and communications. It is not yet known
how much data might have been sensed in the final seconds, before the shuttle came apart, but not transmitted to Earth.

Other evidence:

A portion of Columbia's left wing was recovered. It was further west
than most of the other debris, and it could be a "significant" find,
officials said. NASA planned to test a mockup of the wing in high-
speed wind tunnels, looking at possible patterns of damage,
investigation team member Scott Hubbard said Feb. 11.

A photo of Columbia taken from the Starfire Optical Range shows what
might be a jagged leading edge of the left wing and a plume behind
it. Contrary to early reports, the photo was not taken with any sort
of advance military technology. Story

A military facility in the Southwest captured pictures of Columbia,
taken during the re-entry phase. One image shows what might be
jaggedness on the leading edge of the left wing near the fuselage and
a plume of something trailing the left wing. But officials were not
confident enough in the resolution of the image to draw any
conclusions.

The eerie, dark silhouette of Columbia was photographed at the
Starfire Optical Range (SOR) at Kirtland Air Force Base outside
Albuquerque. Contrary to initial reports, however, it was not taken
with the facility's high-tech equipment. Instead, it was taken by
engineers who had connected a commercial 3 1/2-inch telescope to an 11-year-old Macintosh computer.

The investigation team, meanwhile, asked the Air Force Space Command to review data from spy satellites that might contain useful
information.

Earlier stages of the investigation

NASA has been warning since the day of the disaster that no one
should jump to conclusions. Yet the agency's early and frequent
release of information -- sketchy as much of it was -- had been
compelling and led to near-conclusions in many minds. The open policy
was remarkable compared to how things were handled after the 1986
Challenger explosion. Once incredibly tight-lipped, NASA was thinking
out loud in the initial days of the Columbia investigation. That
changed, however, when the independent investigation board took over.

Until Feb. 4, the case had seemed relatively strong that missing heat
tiles were to blame, related to a root cause of a launch problem. A
bit of insulation foam from the external fuel tank used to boost the
shuttle into space came off just after liftoff and hit the left wing.
It might have ripped off tiles that protect the shuttle from the heat
of re-entry. More likely, officials said, it would have only damaged
the tiles. In fact, during the mission they concluded that there was
no significant damage, which explains why no extraordinary efforts
were mounted to look into the matter further prior to reentry.

Yet once Columbia came apart, the foam seemed a likely culprit.
Thinking on this has see-sawed ever since.

The state of normal matter depends on temperature, which regulates
how fast molecules move and therefore how far apart they are. Plasma, a superhot gas, is an entirely different animal, being electrically charged and very expansive.

PLASMA: What is it?

[IMPORTANT NOTE: Officials now say that the hot gas that surrounded Columbia and appeared to breach the craft had probably not yet reached the plasma state.]

Plasma is sometimes called a fourth state of matter (in addition to
solid, liquid, gas). It's created when gas is superheated and
electrons are stripped out, leaving electrically charged particles.

Plasma occurs naturally in interstellar space and in the atmospheres
of our Sun and other stars. Scientists also create plasma in labs in
order to study emissions from the violent regions around black holes.
A fluorescent lamp is an example of a highly contained plasma.

Plasma reaching as much as 3,000 degrees surrounds the shuttle during re-entry as the craft plows through Earth's atmosphere. Plasma can also be created by impacts from meteoroids or space debris. NASA has not said how Columbia's problem-causing plasma was allowed under the craft's skin, though they know there must have been some sort of hole or gash.

How plasma can damage a satellite. NASA says hot gas, but probably
not plasma, breached Columbia.

Satellite operators worry about impact-generated plasma. Even a
relatively small meteoroid would vaporize upon impact, generating a
cloud of plasma. (IMPORTANT: Small meteoroids hit shuttles frequently
without causing problems other than minor pits in heat tiles.)

On a satellite, however, electrical parts are exposed. Because the
plasma is electrically charged, short circuits can result. An
electrical current flows from one electrical part of the satellite to
another location, through the cloud, and damages an instrument. It is
similar to the damage a lightning strike might cause.

In 1993, during the August Perseid meteor shower, a meteor hit an
Olympus communications satellite. The impact formed a plasma cloud,
and the craft's attitude control system was zapped. By the time
operators could stabilize it, they had depleted all of its attitude-
control propellant and the satellite was lost.

Did Columbia have a "black box" like airliners?

Not exactly. But it did carry a data recorder, found intact in Texas
on March 19, that holds 9,400 feet of magnetic tape containing clues
that have proven helpful in the investigation. Otherwise, the
shuttle's communication system is designed to constantly download
information to ground control. It is not clear how much data might
have been lost in the final moment of the shuttle flight that might
possibly have been retrieved had there been a black box aboard.

In an interview with Computerworld, Steve Schwartz, CTO and founder of UniTrends Software Corp., a backup and crash-recovery company in Myrtle Beach, S.C., explained the technical aspects of the shuttle downloading: "There's a network that uses a protocol named SCPS (Space Communications Protocol Standard), an improvement over TCP (Transmission Control Protocol). The network is IP-based and runs under a virtual LAN; astronauts are able to send/receive e-mail."

Last-minute data that might have gone into a black box might not have been transmitted to the ground, though what actually happened has not been laid out by NASA. Schwartz, however, said the download system is sometime busy acknowledging transmissions and retransmitting previous blocks of data that were not properly received. So sometimes current data sits in a buffer, awaiting its trip to Earth.

NASA did say early on in the investigation that the final 32 seconds
of data transmitted by the shuttle was ragged and not readily
readable. Officials planned to work with the data to try and make
sense of it.

What is the Starfire Optical Range?

The Starfire Optical Range (SOR) is at Kirtland Air Force Base
outside Albuquerque. The facility routinely tracks shuttles. The SOR
houses a 11.5-foot (3.5-meter) telescope designed for satellite
tracking. It also has a 5-foot (1.5 meter) telescope. Both use an
advanced system of adaptive optics (AO), which counteract the
blurring effects of Earth's atmosphere.

The Starfire Optical Range uses a laser to create a fake star in the
sky. The telescope then uses known parameters of the reflected fake
star to compensate for blurring effects of Earth's atmosphere while
making an image of a real object. The facility, below.

Constantly changing turbulent air makes stars and other objects
twinkle, and it also makes them hard to image. The more powerful a
telescope, the more impact the problem has. So instead of one single
mirror, AO uses several, and they are adjusted on the fly during
observations. Adaptive optics is all the rage in astronomy right now.
The primary mission SOR is to develop new optical and imaging
technologies to support Air Force aerospace missions. SOR's larger
telescope, using AO, could spot a basketball 1,000 miles away.

In May 1991, the Department of Defense declassified much of its
research and development of adaptive optics. Laser beacon adaptive
optics technology, developed at the 1.5-meter telescope, has the
potential to revolutionize ground-based astronomy.

The facility also has some clever engineers who took a now-infamous
photo of Columbia during re-entry with a commercial 3 1/2-inch
telescope hooked up to an 11-year-old Macintosh computer.

-- SPACE.COM's Leonard David contributed to this answer

Re-entry: What were the astronauts doing, and were they aware of the problem?

Columbia's communications with the ground were normal, and then they stopped, so little is known about what went on inside the craft
thereafter. A tape of the final communications were released Feb. 12.

The astronauts would have had on their orange pressure suits,
equipped with parachutes that would be of no use at the altitude of
the disaster. They were strapped in tight.

As the shuttle moved into denser atmosphere over California, the
outside of the craft heated up, as always. The craft began to slow,
much like the water in a pool gently slows a diver.

Sally Ride, the first American woman in space, says the process of re-
entry takes about an hour but seems like it flies by.

"When you look out the windows, all you see is orange and pink glow,
seemingly surrounding the shuttle -- almost looks like flames licking
the shuttle," Ride said.

Columbia was more than 200,000 feet up (roughly 38 miles or 60
kilometers) moving at about 12,500 mph (20,120 kph) when
communications were lost.

A final 32 seconds of data was beamed down after voice communications ceased with Columbia. That data has been hard to decipher, however. Todd Curtis, former airline safety analyst with Boeing Co., said: "West of Fort Worth they lost communications but had signals transmitting data. That says to me the voice communication system was off-line but parts of the data communication system were broadcasting. This implies the antennas for broadcasting this data were still intact,'' said Curtis. "You could conclude certain systems, such as power sources, were still running."

That analysis must be considered speculative at this point.

Many people have asked what might have then transpired, and how much time the astronauts might have had to contemplate their fate. This is not really known, and it seems appropriate to not speculate.

Could Columbia have been damaged by a meteor or space junk?

NASA has not ruled this out. A 1997 report by the National Research
Council warned NASA of the threat to shuttles from both natural and
man-made stuff in space [Story].

Small rocks in space pose a threat to all spacecraft, particularly
small satellites. Meteors have caused minor damage on shuttles in the
past, and the phenomenon is well-studied (The Hubble Space Telescope, in space for more than a decade now, is loaded with pits).

The shuttles are designed, in theory, to handle impacts of marble-
sized objects.

EXPLOSIVES: Why does the shuttle carry small pyrotechnic devices?

A space shuttle contains many small explosives used for deploying
certain gear during a mission and for emergencies. If a shuttle's
landing chute ever deployed early, pyrotechnic devices could also be
employed to detach it, for example.

The shuttle's landing gear compartment contains small explosives
designed to deploy the gear if the normal system fails. An accidental
triggering, possibly by heat, could be catastrophic. NASA is now
looking into this possibility as a cause of the Columbia disaster.
But the measured rise of 30 to 40 degrees in the wheel well is not,
for now, seen as a likely trigger.

In some cases, the explosives are integrated into a nut-and-bolt
setup, and are designed to destroy it. A small hole is drilled into a
nut, and something akin to a small firecracker is inserted. A
computer-controlled explosion detonates the charge, which splits the
metal. Referring to the nuts and bolts as "explosive" is a bit
misleading, engineers say. It implies that the firing is uncontrolled
and random. Computers handle the split-second timing of the
detonation.

Foam: What is the foam insulation and why does it fall off?

Foam insulation is sprayed onto the the external fuel tanks in a
gooey form and then becomes hard as a brick but light, like
Styrofoam. It keeps the liquid hydrogen and the liquid oxygen fuel
super cold. Shuttles ride these 15-story tanks during liftoff, then
the tanks separate.

NASA video showed that 81 seconds into the flight, a 20-inch, 2 1/2-
pound piece of the foam fell off and struck Columbia's left wing. The
shuttle Columbia was moving more than at twice the speed of sound.
The impact is thought to have involved a relative speed of no more
than 500 mph.

The foam is fragile enough to have been damaged once in a hailstorm,
forcing a previous shuttle mission to be delayed while the insulation
was repaired. Chunks have come off in flight before, too. They can be
ice-coated, making them heavy projectiles. Columbia sustained damage in this way in 1992 and 1997, and foam struck a booster rocket of Atlantis in October.

"The thing of this is, almost since Day One, the insulation has been
a pain," said Seymour Himmel, a retired NASA executive who served two decades on an aerospace safety panel and looked into the potential dangers of the foam. "Pieces break off,'' Himmel said.

Tiles: What are they made of and what do they do?

Columbia's aluminum skin was covered with more than 20,000 heat-
resistant tiles. They protect the craft against temperatures that can
reach 3,000 degrees Fahrenheit on the leading edge of a wing during
re-entry.

Several have been damaged in past shuttle flights and later replaced.
Some of the tiles are made of silica fibers, derived from sand in a
process similar to making glass.

Much of the Columbia investigation centers around critical reinforced
carbon-carbon (RCC) panels on the forward edge of Columbia's left
wing. The gray, U-shaped RCC panels are bolted in four places to a
flat area on the front of the wing structure. Reinforced carbon-
carbon is a manmade composite material that binds carbon-based
material with other carbon-based material in a molecular structure
designed to withstand re-entry's hottest temperatures, which can
approach 3,000 degrees Fahrenheit. The shuttle's nose cap and a "chin panel" forward of the nose landing gear are made of the RCC material.

Some news reports have called these RCC panels brittle. Composites in
general can be considered brittle, but not in the same sense as
uncooked noodles or grandma's bones. You couldn't go up to an RCC
panel and snap it in two. They are built to be tough -- but they have
had minor surface defects from time to time that have required some
attention during maintenance.

-- SPACE.com's Jim Banke contributed to this answer

If NASA knew something might have been wrong, why did they try the re-entry?

People wonder why the astronauts did not do a spacewalk to fix the
problem before trying to return to Earth. NASA engineers scrutinized
launch video and determined there was nothing to be overly concerned about. They did not know if heat tiles were missing but made the decision that the craft was safe. Subsequent decisions (including not requesting special photographs) were made with this in mind.

At any rate, in this situation, a useful spacewalk would have been
particularly dangerous. There is nothing to hold onto underneath the
wing, where the possible damage was, and the astronauts did not have jetpacks aboard. In any case, no spare tiles are carried aboard
shuttle flights.

Could the damage have been investigated with satellites? Perhaps, but
that was tried during a 1998 mission and the pictures were of little
use.

Could the Columbia astronauts have gone to the orbiting International
Space Station? No. Because Columbia was in a lower orbit than the
ISS -- one designed for the shuttle's science mission -- it didn't
have enough fuel to boost itself up to the ISS.

Could another shuttle have been sent up? Shuttle Atlantis might have
been rushed into service, and if normal testing were skipped, it
might have been in space in a week or so. The Columbia crew had
enough supplies to last through Wednesday, Feb. 5 and might have been able to stretch those supplies a few more days.

What about the robotic arm? Columbia was not equipped with its 50-
foot robot arm because it was not needed for this science-based
mission.

Will human spaceflight continue?

Almost certainly. In fact, an eventual human mission to Mars is
strongly indicated in the newly announced NASA budget for 2004 and in a NASA statement made Feb. 5, just four days after the disaster.

Shuttle flights could resume this fall. On March 12, William Readdy,
NASA associate administrator for space flight, signed a memorandum
establishing a formal "Return to Flight" team. NASA Administrator
Sean O'Keefe indicated that while the cause of the Columbia disaster
needs to be determined for flights start again, the agency needs to
begin preparing for the next launch, which could come this fall. The
Return to Flight team will look at possible ways to improve safety
based on several scenarios now being considered as possible causes of the disaster. Clearly, some measures might prove warranted, while
others would perhaps become moot depending on the outcome of the
investigation.

Amid their grief, space officials inside and outside NASA who have
spoken about the disaster have expressed the need to press ahead.
This is not the first space accident, and unfortunately it probably
will not be the last, but spaceflight is an important component in
advancing modern science and technology, they say.

Further, there is a strong underlying sentiment among people
connected with the space program which holds that the collective
human spirit needs to continue pushing the boundaries of exploration
with an ultimate goal of loosening our ties to this planet. Teachers
will continue to participate in NASA space flights, too, officials
said in the days following the disaster. Even the grieving families
of the astronauts said "the bold exploration of space must go on."

But it will not be easy to start up again. The next shuttle mission
to the space station had been slated for March 1 but is now on hold.
Japan, one of several international partners on the space station,
echoed NASA in saying its astronauts will not fly until the shuttle
fleet is determined safe.

Will shuttles be upgraded or scuttled?

It seems unlikely the existing shuttles will be scuttled. NASA began
preparing, in fact, for the next flight (as of March 12) while
awaiting a green light and, probably, a determination of the cause of
the Columbia disaster. Coincidentally, on Feb. 3, two days after the
disaster, NASA unveiled its budget request for 2004, an announcement
that had been planned for weeks. The budget request was mapped out with White House assistance. It calls for increased spending on
shuttle upgrades with an eye toward keeping them operational until
2025.

Some space experts have called for a new generation of space planes
to be designed and built to replace the aged shuttle fleet. No one
knows if the budget request will stand in the wake of the Columbia
disaster, so all of this is very up in the air for the moment.

What was Columbia's Mission?

Unlike most shuttle missions during the past three years that have
been devoted to building and supplying the International Space
Station, STS-107 was purely dedicated to science and did not travel
to the space station. More than six dozen experiments were being
conducted. Some were a complete loss. The data from many, however, were beamed to Earth. Scientists said the results will lead to
improved human health and save lives.

What is the status of the International Space Station (ISS) and its
crew?

(And doesn't the station need periodic boosts?)

The crew is safe. But eventually astronauts Ken Bowersox and Don
Pettit and cosmonaut Nikolai Budarin must be retrieved, and the best
way to do that is with a shuttle. On Sunday, Feb. 2, a previously
planned launch of an unmanned Russian supply ship, called Progress,
went off as scheduled. It docked with the station two day later and
the station crew unloaded one ton of food, fuel and other supplies.

They crew now has enough supplies to last through late June. The
earliest they would likely come home is early May after a fresh Soyuz
spacecraft is launched with a new crew. But the crew says they are
prepared to stay a year if needed. A shuttle launch had been
scheduled for March 1 to swap ISS crews, but that is on hold. NASA
must now decide if and when it is safe to launch another shuttle.
Aboard the ISS are.

If need by, the station crew could return in a Russian Soyuz,
a "lifeboat" capsule that is always affixed to the orbiting outpost.
NASA space station official Michael Kostelnik said that a fresh Soyuz
would be sent to the station in April as planned. If needed, the
Soyuz ships could swap crews until NASA's shuttle fleet is certified
to fly again.

Doesn't the station need periodic boosts? Yes, sometimes by a dozen
miles or so. Otherwise it would eventually fall to Earth. You might
recall that Skylab burned up in the atmosphere on July 11, 1979 after
its orbit deteriorated for 5 years. The Compton telescope and the
Russian Mir space station met similar fates. The Hubble Space
Telescope has no onboard boosters and is lifted back into higher
orbit during shuttle servicing missions. The ISS boosts can be
supplied by shuttles and the Russian Progress supply ships. The
station was boosted Feb. 11 or 12. The next boost would come probably in or around June. Progress supply ships always bring fuel and do the reboosts. Shuttle can too. -- SPACE.com's Jim Banke contributed to this answer.

Meanwhile, NASA said on Feb. 12 that science experiment aboard the
station continue. Basic and applied research is being conducted in
biology, physics, chemistry, ecology, medicine, materials science,
manufacturing and the long-term effects of space flight on humans.
And on Feb. 14, a report said the United States and Russia would
cooperate to keep the station going. Russian officials said they
would build extra $22 million supply ships as long as othr partners
in the 16-nation space station project would pay for them.

What should I do if I find Columbia debris?

Debris presumed to be from the shuttle Columbia landed in the
driveway of Susie and Art Patterson's home in Nacogdoches, Texas. It
is about a foot long.

NASA and the indpenedent investigation board are both interested in
obtaining pictures and videos of the event. The Gehman Board has a
Web site, http://www.caib.us/, for information about the board's
activities and to learn how to contact the board directly if you have
any debris reports to make, or theories to offer.

You can also report debris or images to NASA at this phone number:
281-483-3388 or (936) 699-1032. Text reports and images should be e-mailed to: columbiaimages@nasa.gov or nasamitimages@jsc.nasa.gov.

Do not touch any debris you find. NASA officials have warned
repeatedly that the debris "may be dangerously contaminated with
toxic substances and cause serious injury if handled. Individuals who
think they may have come in contact with shuttle debris should take a
shower with soap and water and then seek medical attention.

NASA: "Individuals are advised to avoid all additional contact with
the suspected shuttle material. Clothing that may have come in
contact with the suspected debris should be removed with care to
avoid skin contact with cloth that may have been contaminated. Place
the clothing in a plastic bag for later analysis. If your physician
has any questions, please have him or her contact the NASA Emergency Action Center at 281-483-3388."

Also dangerous are pyrotechnic devices that the shuttle carries and
which may remain unexploded.

NASA wishes all debris be reported to them, so that the pieces can be
used to help determine what caused the disaster. The space agency
also warns that the debris is government property, and local law
enforcement officials have been asked to aid in recovering it.

In fact, two Texans were arrested on federal charges they stole
pieces of the debris and a Texas law enforcement official was charged
in a separate case.

What is being done for the astronauts' families? And how can I send
sympathies?

A fund is being set up. The Space Shuttle Children's Trust Fund was
established with the support of NASA after the 1986 Challenger
disaster. The fund, which raised $1 million, will now work to raise
money for Columbia families.

NASA held a private memorial for the astronauts Feb. 4 at the Johnson
Space Center. President Bush and the first lady Laura Bush were
accompanied on Air Force One by Neil Armstrong, the first astronaut
to walk on the moon. Former senator and astronaut John Glenn and his
wife, Annie, also attended, as did NASA Administrator Sean O'Keefe.
Kathie Scobee Fulgham, whose father died on the space shuttle
Challenger, was to speak to the children of the Columbia astronauts
at the memorial.

A memorial ceremony for Columbia's astronauts was held Feb. 7 at the
Kennedy Space Center. Florida Governor Jeb Bush, Administrator
O'Keefe and former astronaut Robert Crippen, Columbia's first pilot
on its maiden flight, STS-1, on April 12, 1981, attended.

More Questions

Could Columbia have been hit by an electrical discharge?

This should be considered highly speculative. A report last week in
The San Francisco Chronicle says federal investigators (not the NASA
team) are looking into this possibility. Data are being reviewed for
evidence any high-altitude jets or sprites, which commonly occur
above thunderstorms and are known to shoot nearly into outer
space. "We're working hard on the data set," said Alfred Bedard, a
scientist at the federal Environmental Technology Laboratory in
Boulder, Colo. The lab is providing data to NASA, according to the
story.

The Chron says NASA administrators confirmed that a photograph
showing an odd streak of light, taken by a San Francisco amateur
astronomer, is being evaluated by Columbia crash investigators.
Shuttle investigators are not certain if the oddity is real or an
artifact.

How did so much debris survive re-entry heat and make it to the
ground?

Meteors often burn up before they reach the ground. But many survive.

What happens depends on many factors:

Meteors are not typically in orbit around the planet. They come from
elsewhere in the solar system and crash into our atmosphere at
incredible velocities. The shuttle was traveling at about 12,500 mph.
A meteor can reach speeds of 160,000 mph (72 kilometers per second)
relative to Earth (many move at about half that speed).
The heating that can lead to vaporization of a meteor begins around
60 miles up. The shuttle was already down to around 40 miles altitude
when problems began.

Meteors larger than baseballs frequently survive. Columbia's wreckage
involved a lot of good-sized pieces.

Finally, natural meteors are hunks of stone and metal, often very
loose agglomerations with surface roughness that enhances the
tendency to vaporize. Columbia's parts were designed for strength and
stability and were often smooth.

Could the Hubble Space Telescope have taken pictures of the shuttle?
No. Hubble is not equipped for the task of imaging a moving target.
And it is so powerful that to image the entire Moon would require 130
separate exposures. [See what I mean in this Moon photo gallery]

Could the flight have been aborted before the shuttle entered outer
space?

In theory, yes. The shuttle can abort and land before it reaches
orbit. But NASA did not suspect there was a problem until after the
craft was in orbit and the launch video was reviewed (and then
officials determined there was no problem). Once in orbit, returning
earlier would likely have yielded the same result, assuming the
damage had in fact been done during launch, though it has not been
determined for whether the damage, in part or total, occured during
launch, in flight, or at re-entry.

Does the shuttle come back to Earth on the same path each time?

No. This mission involved a relatively low orbit. Missions to the
International Space Station go higher, and due to the different
orbit, those shuttles typically come back to Earth over Mexico and
the open waters of the Gulf.

Were puffs of smoke in the contrail signs of an explosion or a result
of the structure falling apart?

The puffs are almost surely telltale of something. But NASA has not
yet determined what sorts of debris caused the earliest puffs seen in
video, nor what specific process led to things falling apart. An
amateur video shows what may be some of the earliest signs of
problems over Reno, Nevada.

Was Columbia landing at the time that was scheduled at the outset of
the mission?

Yes. Everything was going according to plan, and officials have said
this seemed like one of the smoothest missions ever, up to the point
of the disaster. Everyone in the space community was surprised to
lose a shuttle upon re-entry; launch is considered the more dangerous
event by far.

Can the external fuel tank be recovered and studied?

No. The external fuel tank (called ET by NASA) stays with the shuttle
until about 9 minutes after launch. It then separates, falls back,
and burns up as it comes through the atmosphere. This has confused
some people because another part of the launch system is retrieved.
Solid rocket boosters (SRBs), which provide most of the thrust for
liftoff, detach about 28 miles (45 kilometers) up while the shuttle's
main engines continue firing. The SRBs fall into the ocean off Cap
Canaveral and are picked up, refurbished and re-used.

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