Weird lifetime issue

life.rs

md_ref = line.split_iter(' ')
                        .transform(|s| s.to_owned())
                        .collect::<~[~str]>()[2]
                        .iter()
                        .collect::<~[char]>()
                        .chunk_iter(2)
                        .transform(|cs| {
                            let s = str::from_chars(cs);
                            println(s);
                            u8::from_str_radix(s, 16).get()
                        })
                        .collect();


// Error 
nist.rs:117:29: 122:25 error: borrowed value does not live long enough
nist.rs:117                     md_ref = line.split_iter(' ')
nist.rs:118                         .transform(|s| s.to_owned())
nist.rs:119                         .collect::<~[~str]>()[2]
nist.rs:120                         .iter()
nist.rs:121                         .collect::<~[char]>()
nist.rs:122                         .chunk_iter(2)
nist.rs:117:29: 128:35 note: borrowed pointer must be valid for the method call at 117:29...
nist.rs:117                     md_ref = line.split_iter(' ')
nist.rs:118                         .transform(|s| s.to_owned())
nist.rs:119                         .collect::<~[~str]>()[2]
nist.rs:120                         .iter()
nist.rs:121                         .collect::<~[char]>()
nist.rs:122                         .chunk_iter(2)
            ...
nist.rs:117:29: 123:25 note: ...but borrowed value is only valid for the method call at 117:29
nist.rs:117                     md_ref = line.split_iter(' ')
nist.rs:118                         .transform(|s| s.to_owned())
nist.rs:119                         .collect::<~[~str]>()[2]
nist.rs:120                         .iter()
nist.rs:121                         .collect::<~[char]>()
nist.rs:122                         .chunk_iter(2)
            ...
nist.rs:117:29: 119:47 error: borrowed value does not live long enough
nist.rs:117                     md_ref = line.split_iter(' ')
nist.rs:118                         .transform(|s| s.to_owned())
nist.rs:119                         .collect::<~[~str]>()[2]
nist.rs:117:29: 122:25 note: borrowed pointer must be valid for the method call at 117:29...
nist.rs:117                     md_ref = line.split_iter(' ')
nist.rs:118                         .transform(|s| s.to_owned())
nist.rs:119                         .collect::<~[~str]>()[2]
nist.rs:120                         .iter()
nist.rs:121                         .collect::<~[char]>()
nist.rs:122                         .chunk_iter(2)
nist.rs:117:29: 121:25 note: ...but borrowed value is only valid for the method call at 117:29
nist.rs:117                     md_ref = line.split_iter(' ')
nist.rs:118                         .transform(|s| s.to_owned())
nist.rs:119                         .collect::<~[~str]>()[2]
nist.rs:120                         .iter()
nist.rs:121                         .collect::<~[char]>()